In networking, social media and other occasions, some words with positive meanings will derive from the expression of negative emotions or evaluation. “Xiexie” has developed a use to express negative emotions or comments in social media and other contexts. This paper holds that this new usage belongs to implicit negation, which is essentially a false politeness strategy used to highlight the speaker’s subjective feelings and achieve some indirect speech act. Based on the corpus, this paper analyzes the structural characteristics of “xiexie”, and discusses its pragmatic function and evolutionary mechanism. From the perspective of speech act, this paper summarizes the pragmatic functions of this kind of “xiexie”, which can be roughly established into three categories: signaling function, cathartic function and teasing function. The evolutionary mechanism of negative emotion or evaluation is false politeness strategy and communicative subjectivity. The study of the implicit negative usage of “xiexie” provides a new Angle for the study of a class of words that indicate negative emotion or evaluation with positive meaning in communication.