首尾句作文是根據段首（尾）句續寫短文。段首句作文也稱主題句作文，因為作文題中所給的段首句往往是段落主題句。其特點是以題目為中心，一般情況下將文章分為三個段落，每段首句即為該段的主題句（topic sentences）。考生要按主題句的要求組織材料，提出論據，用一些輔助句（supporting sentences）來支持或說明主題句，寫英文段首句作文要注意：所寫的內容要緊扣主題，輔助句應圍繞段首句續寫。保證段內每個句子的內容與段首句緊密展開各個段落，如：例證、因果、定義、比較對比、程序等。要注意句與句之間，特別是段首句與輔助句之間的自然銜接。另外，所給的段首句有時是一個完整的句子，有時不是一個完整的句子，只是句子的一部分，這就要求考生一定要審好題。找出其中表示中心思想的關鍵詞，圍繞這些關鍵詞去擴展、描述或說明。
[例1]directions ：for this part，you are allowed 30 minutes to write a composition about women in the modern world in three paragraphs. you are given the first sentence of each paragraph and are required to develop the idea in completing the paragraph； your part of the composition should be about 100 words， not including the words given. remember to write clearly.
[范文]
　　women in the modern world
　　women are playing an increasingly important role in society. successful women who are government officials,writers, scientists,doctors and teachers can be found everywhere. it is true that many jobs that once were dominated by men can be done well by women.
with the changes in their social role，women?s position in the family has been improved as well.the husband is no longer the only bread maker in the family and the wife no longer lives on others.they share comforts and hardships with each other.
　　in spite of these changes, the liberation of women has not been completely realized. women still face many difficulties and obstacles due to traditional roles and limited economic strength.women still have a long way to go in their struggle for complete equality with men.
第一段首句是講婦女在社會上的作用，因而續寫的內容緊緊圍繞婦女的社會作用，比如，婦女可以是政府機關的工作人員、科學家、教師等；第二句的段首句是關于婦女在家庭中的地位也提高了，續寫的內容也是有關夫妻患難與共；第三句的段首句是講婦女解放仍然任重而道遠，續寫的部分提出了婦女所面臨的問題，整個續寫的部分緊扣段首句。
[例2]directions ：write a composition about what would happen if there were no power in three paragraphs， you are given the first sentence or part of the first sentence of each paragraph：
1?ever since early this century，electricity has become an essential part of our modern life.
2?if there were no electric power，……
3?therefore，……
[范文]
　　what would happen if there were no power
　　ever since early this century, electricity has become an essential part of our modern life. it has played a decisive role in the modern world. everybody admits that development of our civilization depends on electricity.
　　if there were no electricity power, our modern world would be in trouble. for instance, all the wheel would stop because without the power the machine would cease working. and all the electrical equipment life would be impossible and in a great mass without electricity.
therefore, we should make better use of elective power. on the other hand, we should educate people to economize on electricity and not to waste energy resources. at the same time we must do our best to exploit more electric resources to meet the requirements of human beings.
第一段的段首句是講電已經成為人們現代生活中必不可少的部分，因而接下來的續寫部分應強調它的重要性。第二段的段首句提出如果沒有電的假設，下面列出沒有電將會出現的麻煩。最后一段指出我們應該節約用電，開拓更多的電力資源。