Research in L2 writing transfer has drawn scholarly attention both home and abroad with the emergence of writing-across-the-curriculum movement and EAP courses in recent years. However, there are various definitions of writing transfer; researchers opinions regarding the mechanism of writing transfer are also widely divided. This paper examined the definitions and theoretical discussions of writing transfer from linguistic perspective, cognitive perspective, sociocultural perspective and dynamic systems theory perspective. Besides, empirical studies in the international context within the past 40 years were synthesized. In the end, this paper summarized the achievements and problems in the existing studies with the purpose of providing reference for L2 writing instruction and research in China.