As the top priority in language teaching, vocabulary teaching has attracted the attention of the academic circles.As an important module in advanced teaching, the teaching of short word has also been valued by many scholars. Synonyms have always been a difficult problem and a key problem for learners and teachers. Therefore, the author selected a pair of synonyms, “对比” and “对照” with high use frequency and high error rate, as the research objects. This article starts from the interpretation of “对比” and “对照” in the three dictionaries of “现汉”, “规范” and “应用”, first compares the definitions of “对比” and “对照” in the same dictionary, and then compares the definitions of “对比” and “对照” in the three dictionaries respectively. It is found that the definitions in the three dictionaries of “现汉”, “规范” and “应用”, although they are roughly the same, but they are not exactly the same. I also found that there were also great differences in the discrimination contents given in different dictionaries. Therefore, when learning or when teaching, relying completely on dictionaries can not completely solve the problem.By using the analysis of “contrast” and “control”. The synonyms and discriminatives of “对比” and “对照” were analyzed. and the similarities and differences were found, and the requirements of “对比” and “对 照” were interchangeable.