The paper gives an overview of learner corpora and their application to second language learning and teaching. It is proposed that there are four core components in learner corpus research, namely, corpus linguistics expertise, a good background in linguistic theory, knowledge of SLA theory, and a good understanding of foreign language teaching issues (Granger, 2009). Based on the above components, the present paper first introduces learner corpora, then reviews literature concerning the application of corpus linguistics to SLA by means of contrastive interlanguage analysis, and at last discusses the relationship between learner corpora and foreign language teaching.