Abstract: As an important theory for language learning, competition model has developed from the classic version to the unified competition model. Both of them proposed some theoretical points on language transfer, stimulating some empirical studies. These achievements, however, remain largely unknown to SLA field in China. In order to fill in this gap, this paper reviews the theoretical points and empirical studies in the two phases of competition model with a special focus on language transfer, and finally points out new directions for future research. Compared with the classic version, the united competition model provided more systematic accounts of language transfer in a broader scope. Similarly, the empirical studies within the newer model surpassed those in the classic version. To be specific, they investigated more arenas and cultural factors in diverse L2 learners through a combination of off-line and online methods. But critically speaking, these studies are not flawless in terms of content and methodology, thus calling for further improvements in future research.