| In the 1950s, the American applied linguists Fries and Lado began to study the errors of SLA systematically. In addition, they established the preliminary EA theory. At first, the focus of the theory is to analyze and evaluate students'errors and language levels from the teachers'points of view. Then in 60s and 70s, Corder developed the theory in depth. The focus of the research changed from the external perspective into the internal point of view, that is, to see errors from the learners' points of view. Learners'errors can reflect their language levels. EA can enable linguists and teachers to reveal the existing problems in language learning through observation, classification and analysis. While in the five skills of English, writing plays a very important part and it is also the most complicated part. The level of writings can reflect the overall quality of learners. However, writing teaching is always the weak link. As a result, students often made many errors when writing compositions. In the study, the writer randomly chose 100 copies of students' compositions in their exams in DaLian Neusoft Institution of Information to do a case study. The writer mainly used EA Theory to describe and analyze the lexical errors in students'writings as well as hunting for the potential causes of these errors. The result showed that there were many errors when students wrote compositions and lexical errors took up the highest proportion. These errors mainly included spelling errors, wrong choice of words, collocation errors and literal translation errors. The causes of those errors were complex, the causes were mainly due to interlingual causes; intralingual causes; lack of practice and inaccurate teaching. Finally based on the major findings, the writer suggested that teachers should fully consider the causes of students' errors and then designed teaching plans as well as adopted teaching methodology accordingly. The teachers should also study more useful error-correcting strategies. Only in this way, could they achieve their teaching goals. |