Humor is a phenomenon that permeates every pore of human life and all-encompassing in human communication. Studies on humor have triggered the interest of scholars from ancient philosophers such as Plato, Aristotle to recent scholars like Bergson and Freud. Most studies on humor tend to be approached from physiological, psychological and sociological perspectives.This thesis focuses on the study of humor in Chinese sitcoms. I use Chinese sitcoms as a source of data for analysis largely because of the convenience of data collection. It is also due to the fact that other forms of humorous text can hardly provide sufficient examples of verbal humor which I intend to study.The study of humor in sitcoms in this thesis is conducted from the pragmatic perspective through the employment of three influential theories in this field: the co-operative principle (CP) by H.P Grice (1975), the relevance theory (RT) by Sperber & Wilson (1986/1995), the politeness principle (PP) by Leech (1983) and face theory by Brown & Levinson(1978).Grice’s CP holds that all successful human communications comply with the cooperative principle either on the superficial or inferential level. But from the two case studies of the selected dialogues from the sitcoms, it is found that humor is generated when certain maxims under CP are violated. The issue in question is that the violation does not necessarily lead to any conversational implicature, but still renders smooth communication and the occurrence of humor.The limitations of Grice’s theory in interpreting humor could be eluded within the theoretic framework of RT. When the interlocutor is communicating in violation of the maxim of relevance, he may be still communicating something relevant. According to Sperber & Wilson, the presumption of optimal relevance is specified as "ostensive stimulus is the most relevant one compatible with the communicator’s abilities and preferences." Therefore, a seemingly irrelevant utterance may still be considered of optimal relevance if it is compatible with the communicator’s preference to be humorous.Understanding of either the explicit or implicit meaning of utterances depends a great deal on the contextual assumptions. The contextual assumptions are not confined to the immediate physical context provided by the preceding utterances, but rather determined by the general factors in one’s cognitive environment. When the newly-presented information interacts with the old information and the evolved contextual assumptions, the communicator will be able to draw his inferences. In the process, the communicator will invariably choose the contextual assumptions most relevant to his cognitive environment because human cognition tends to use the least processing effort to achieve the largest contextual effects. What the humor creator is able to do is to take advantage of this tendency and make deliberate deviation from it to elicit laughter. Though the processing involves more efforts, the contextual effects are larger and they make the source of humor.Leech’s theory of politeness throws some new light on the issue of humor interpretation. The maxims of politeness supposed to govern human behavior and ensure the equilibrium of interpersonal relationship are intentionally violated for the sake of humor generation.According to Brown & Levinson, as an attempt to avoid the threatening of the negative or positive face of an interlocutor, certain strategies are adopted. "Off-record" politeness may become another source of humor. In some contradictory cases, when "bald-on-record" face-threatening acts are performed in the stead of politeness strategies to diminish the face-threat, the humorous effect comes into being just because this kind of deliberate face-threatening is more possibly taken as a joke to get laughter.