介词是托福考试试题中比较活的词性，而且具有一定的难度。中国考生一向对介词感到束手无策，因为英文介词种类繁多且词意多变。不过，托福考试涉及的有关介词的题目重复性很强，而且有规律可循。只要考生善于总结、记忆，还是可以保证得满分的。
介词的题目主要分布在Written Expression(16-40题)中，命题焦点：
(1)含有介词的固定短语，(2)含有特定含义的介词误用
介词常考题型及解题要点
1.含有介词的固定短语：短语或词组中的介词不能随意更换或省略
全真例题分析
(1)Most aquatic animals breathe by means external respiratory organs called gills.
答案：C 正确的短语为by means of，其中的介词of不能省略
(2) Speed refers only toward the rate of mution without specifying any direction of motion.(94.8)
答案：A 正确短语形式为refer to
(3) Historical geology deals about data on the development of the Earth gathered from the study of rocks, which are analyzed to determine their age and composition. (93.8)
答案：A正确短语式式为deal with
(4)The diamond is the only gemstone composed with just one chemical element, carbon.
答案：A 正确短语形式为Be composed of
(5) Best known for his research in statistical mechanics and meson physics. Chen Ning Yang shared the Nobel Prize in 1957 to another physicist from the United States, Tsung-dao Lee.
答案：C 正确的短语搭配为share…with
(6)The doctrine of eminent domain is based the legal tradition that all real property is subject to the control of the state.
答案：A 正确的短语形式为be based on其中的介词on不能省掉。
2. 介词用错
解题要点：介词与后面的名词通常有固定的搭配习惯，或有特定的语意功能，不能随意更换。通常，介词必有含义，不同的介词会使整个句子表达不同的意思。当A、B、C、D四个选择答案中出现单独划线的介词，应首先考虑它是否使用正确。
全真例题分析
(1)Scientists claim that an individual can function from about three days when totally deprived of sleep.
答案：C from应改用for，表示动作延续的时间应用介词for
(2) Canadian scarlet-clad guards and mounties with horseback are part of the summer scenery in Ottawa.
答案：B with改为on，“骑在马背上”应用介词on表示位置
(3) During eclipses of the Sun, the Ojibwa Indians of North America shot flaming arrows inside the sky to rekindle the light.
答案：C inside改为into，介词into表示的动作性；shot…into the sky，天空无边无沿，不能用介词inside来修饰
(4) Wild elephants are almost continuously waving their trunks. Both up in the air and down aside the ground.
答案：D aside改为on，on the ground 是固定介宾搭配。Ground 没有边沿，无法用aside来修饰
(5) Recent studies have shown that air into a house often has higher concentrations of contaminants than heavily polluted air outside.
答案：A into改为in，into强调动作，而in表示的是静止的状态。“房间里面的空气”只能用in来表示
(6) The early use of a complete steel frame for towering buildings appeared in the first skyscraper, built on Chicago in 1883.
答案：D built on改为built in，城市名前面只能用介词in来修饰
