Based on Flavell's meta-cognitive theory， this paper uses students' written comments of peer reviewing as the research data to study the relevance of peer reviewing to the metacognitive affects that second language students have about their English writing． Through the analysis of 210 students' peer revision comments， it has been found that L2 students are positive to the peer reviewing． And also， the written comments from peer reviewing can reflect a close connection between the metacognitive affects and the L2 students English writing． This finding has some implications for English teaching and learning of writing．