This study analyzes researches of Chinese English learners English intonation，finding that Chinese learners do have a lot of problems in tonality，tonicity and tone patterns，which could lead to communication breakdown．Then this study analyzes the reasons for this phenomenon from the perspective of Cognitive Psychology concerning explicit and implicit processing of English input，and cognitive processing of English output． The conclusion is that Chinese learners do not have enough processing of English intonation in working memory; English intonation input does not get processing in cognitive interface，so that it is very difficult to get tuned and integrated into the knowledge system by implicit learning in the subsequent input processing．This results in Chinese English learners not having enough implicit knowledge of English intonation; while making English output，students still use implicit knowledge of Chinese intonation．