Writing is commonly used to assess not only students’ language skills but also their learning in many academic areas. Responses to students’ writing greatly influence attitudes to writing and motivations for further writing. This paper begins with a review of the theoretical and research literature focusing on peer feedback in second language writing classes. Four theories which support peer feedback as an effective teaching method are reviewed: cognitive writing process theory, social-construction theory, and two second language acquisition theories - the input hypothesis and the output hypothesis. Relevant research is reviewed from three perspectives: the literature against peer feedback, literature supporting peer feedback and literature advocating training of students for peer feedback. After exploring English education in China and anticipating potential problems in implementing peer feedback in EFL writing classes at the tertiary level, the paper concludes that with appropriate training, it is feasible to incorporate peer feedback into university-level English writing classes in China. Various implications and applications of peer feedback are suggested.