Abstract: The past thirty years has witnessed the rapid development of language testing in terms of theory, practice and methodology.In this area, L.F.Bachman has been one of the leading figures who have made great contributions to language testing.This paper offers a comprehensive picture of Bachman's language testing theories, including his viewpoint on language competence, testing validation and the latest development, authenticityf, actors affecting the performance of test takers and the relationship between individualistic characteristics and testees'performance.In addition, he also explores the relationship between Second Language Acquisition and language testing It is hoped to outline the general orientation of language testing over the past three decades with the demonstration of his theories.