主要有三点：1.句子长，长度超过30单词的长句在每篇文章中保持在10句左右;2.概念难，句中往往含有很多“诡异”的陌生学术概念;3.结构异，英文中的特定语法结构如倒装，强调，修饰语后置等等。
快速理解复杂长难句是托福阅读考试得分最重要的能力。比较近10年来的考试难度，最明显的趋势就是句子结构的复杂冗长程度明显递增。纵观文章阅读考察的几个层次可发现：比句子微观的单词含义理解，只要认真准备就不是难点;比句子宏观的段落含义理解，弄懂主旨往往不难。而相对地，长难句的阅读相对需要更多技巧，考场上经常出现反复多遍阅读仍不能理解句子大意的情况，从而成为了阅读理解和得分的瓶颈。
接下来我们从句子结构、翻译、分句等方面来进行一些长难句实例解析。
1. The end of the nineteenth century and the early years of the twentieth century were marked by the development of an international Art Nouveau style, characterized by sinuous lines, floral and vegetable motifs, and soft evanescent coloration.
(特殊结构 marked by...——以...为标志、characterized by...——特征是)
19 世纪末与 20 世纪早期以一种国际新艺术风格的发展为标志，这一艺术风格的特征是：线条弯曲，以花卉和果蔬为主题，颜色柔和飘逸。
分句 1: The end of the nineteenth century and the early years of the twentieth century were
分句 2: marked by the development of an international Art Nouveau style
分句 3: characterized by sinuous lines, floral and vegetable motifs, and soft evanescent coloration.
2 和 3 并列 ，1 和 2、3 嵌套
2. Although its influence continued throughout the mid 1920’s, it was eventually to be overtaken by a new school of thought known as Functionalism that had been present since the turn of the century.
(特殊结构 known as...——被称为)
尽管其影响在整个20世纪20年代中期继续存在，但最终还是被世纪之交以来就存在的新的思想流派 —— 功能主义所替代。
分句 1: Although its influence continued throughout the mid 1920’s
分句 2: it was eventually to be overtaken by anew school of thought known as Functionalism
分句 3: that had been present since the turnoff the century.
1 和 2 并列， 2 和 3 嵌套
3. This new design concept, coupled with the sharp postwar reactions to the styles and conventions of the preceding decades, created an entirely new public taste which caused Art Nouveau types of glass to fall out of favor.
(特殊结构 coupled with...——加上)
这一新的设计概念，加上战后对过去数十年风格与传统的强烈反应，产生了一种全新的公众品味,使得新艺术类型的玻璃不再受人欢迎。
分句 1: This new design concept
分句 2: coupled with the sharp postwar reactions to the styles and conventions of the preceding decades, created an entirely new public taste
分句 3: which caused Art Nouveau types of glass to fall out of favor.
1 和 2 并列 ，2 和 3 嵌套
4. Although leaders are often thought to be people with unusual personal ability. decades of research have failed to produce consistent evidence that there is any category of “natural leaders.”
(同位语从句 evidence that...)
尽管领袖常被人认为是个人能力非比寻常的人，但是数十年的研究迄今未能提供一致的证据表明存在任何“天然领袖”类型。
分句 1: Although leaders are often thought to be people with unusual personal ability
分句 2: decades of research have failed to produce consistent evidence
分句 3: that there is any category of “natural leaders.”
1 和 2 并列 ，2 和 3 嵌套
5. Furthermore, although it is commonly supposed that social groups have a single leader, research suggests that there are typically two different leader ship roles that are held by different individuals.
(复合句)
而且，尽管一般人认为社会团体只有一位领袖，但是研究表明通常存在由不同个体担任的两个不同的领导角色。
分句 1: Furthermore, although it is commonly supposed that social groups have a single leader
分句 2: research suggests
分句 3: that there are typically two different leader ship roles that are held by different individuals.
1 和 2 并列 ，2 和 3 嵌套
6. Expressive leaders are less concerned with the overall goals of the group than with providing emotional support to group members and attempting to minimize tension and conflict among them.
(特殊结构 less...than...——较少...较多...)
善于表达的领袖较少注重团体的整体目标，较多注重为团体成员提供情感支持，并尽力减少内部纷争和冲突。
分句 1: Expressive leaders are less concerned with the overall goals of the group
分句 2: than with providing emotional support to group members
分句 3: and attempting to minimize tension and conflict among them
1 和 2、3 并列， 2 和 3 并列
7.Equally important is the fact that the execution of multiple—step tasks is accomplished in a series—parallel sequence.
(倒装句)
同样重要的是一个事实：多步任务是按照系列—平行序列完成的。
分句 1: Equally important is the fact
分句 2: that the execution of multiple — step tasks is accomplished in a series — parallel sequence
1 和 2 嵌套
8. But these factors do not account for the interesting question of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth.
(Of 结构作定语: of how there came to be such a concentration of pregnant ichthyosaurs...)
但这些因素并不能解释这个有趣的问题：为何在一个特定的地点会如此集中地出现即将临产的怀孕鱼龙群。
分句 1: But these factors do not account for the interesting question
分句 2: of how there came to be such a concentration of pregnant ichthyosaurs in a particular place very close to their time of giving birth
分句 1 是嵌套分句，分句 2 是 of 结构作后置定语修饰说明 question 的内容。
9. In the seventeenth century the organ, the clavichord, and the harpsichord became the chief instruments of the key board group, a supremacy they maintained until the piano supplanted them at the end of the eighteenth century.
(同位语 a supremacy)
17 世纪时风琴、敲弦琴和拨弦琴成为键盘乐器类的主要成员，这种至高无上的地位一直由它们保持，直到 18 世纪末被钢琴所取代。
分句 1: In the seventeenth century the organ, the clavichord, and the harpsichord became the chief instruments of the key board group,
分句 2: a supremacy they maintained until the piano supplanted them at the end of the eighteenth century
分句 2 是分句 1 的同位语从句，用来修饰说明分句 1 中的 the chief instruments of the keyboard group
10. A series of mechanical improvements continuing well into the nineteenth century, including the introduction of pedals to sustain tone or to soften it, the perfection of a metal frame and steel wire of the finest quality, finally produced an instrument capable of myriad tonal effects from the most delicate harmonies to an almost orchestral fullness of sound, from a liquid, singing tone to a sharp, percussive brilliance.
(介词结构 from...to...作定语)
持续到19 世纪的一系列机械上的改进，包括引入踏板以维持音调或使其柔和，改善金属框架，以及使用最佳性能的钢丝，最终产生了一种具备无数音调效果的乐器 —— 这些效果涵盖了从最精致的和声到几乎全部的管弦乐音响，从明快流畅的吟唱音调到尖锐的打击乐器的恢弘气氛。
分句 1: A series of mechanical improvements continuing well into the nineteenth century
分句 2: including the introduction of pedals to sustain tone or to soften it
分句 3: the perfection of a metal frame and steel wire of the finest quality
分句 4: finally produced an instrument capable of myriad tonal effects
分句 5: from the most delicate harmonies to an almost orchestral fullness of sound
分句 6: from a liquid, singing tone to a sharp, percussive brilliance
本句的真正的主句结构其实是由分句1和分句4构成，即 A series of mechanical improvements continuing well into the nineteenth century finally produced an instrument capable of myriad tonal effects;
分句2和分句3并列修饰，说明分句1中的 A series of mechanical improvements;
而分句5和分句6并列，修饰说明了分句4中的 an instrument capable of myriad tonal effects