The use of collocations will affect the accuracy and idiomaticity of a piece of writing. The present paper analyzes and traces the causes of two types of lexical collocation errors by advanced learners in Chinese Learners English Corpus (CLEC): verb + noun and adjective + noun collocation errors. It is found that for the verb + noun collocation errors though it is the noun decides the meaning of the collocation, the inadequate combinations of verb+ noun undermines the accuracy of writing to a large extent. For the adjective+ noun collocation errors, L1 interference is a major cause. It is believed that exploring learner corpus can be an effective way to improve learners' writing. Corpus allows students to observe an extensive data, which help them understand collocations and finally master them. Utilizing corpus to explore collocations will solve the problem of inaccurate expression in learner's writing.