From my previous teaching experience I have found that a lot of students have been misusing the comparative degrees of adjectives. There are three major types of the mistakes they have made: using “more” and “er” at the same time; adding “er” to irregular adjectives; or mistakenly making up a comparative degree for adjective which do not have one. This problem has brought out my interest to do further research. I’ m keen to find out whether this kind of mistake is commonly made by all Chinese speaking English learners. Therefore I have undertaken a research on the Chinese Learner English Corpus (CLEC); I have found more than 300 examples of similar mistakes from this research. The aim of this project is to prove “misusing the comparative degree of adjectives” is one common mistake made by Chinese speaking English learners. In order to reach this objective the major categories of errors recorded in the CLEC will be outlined. And then relevant comparisons will be made with data I have collected from Brown (American English)--corpora of English speakers. An exercise which contains two sets of questions has been designed to help students reviewing their knowledge on the comparative degrees of adjectives.