The present study focuses on the deliberate use of vague language in Chinese verbal communication, which is viewed as a communicative strategy and termed as "Pragmatic Vagueness". It mainly belongs to a qualitative study based on the data collected from literary works, TV series, and daily conversations. The conceptual framework is constructed on the basis of Jef Verschueren’s (1999) Linguistic Adaptation Theory. The investigation concentrates on the variability, adaptability, and functionality of pragmatic vagueness.Being a strategy of communication, pragmatic vagueness relies on various linguistic structures to realize its functions. Thus, the addresser needs to manipulate her language so as to choose a proper linguistic structure which can carry out her strategy. Through careful observation of the data, we generalize three ways of linguistic manipulation involved in the strategy of pragmatic vagueness, namely, enhancing the context-dependency of the utterance, broadening the interpretative range of the utterance, widening the distance between the idea and its way of expression. Furthermore, some specific linguistic devices are included in each category. Thus, the variability of pragmatic vagueness is demonstrated through its ways of linguistic manipulation.If the process of linguistic manipulation answers the question of how pragmatic vagueness is used in verbal interaction, the discussion of the adaptive process deals with the problem why pragmatic vagueness is chosen in a specific situation. It is found out that pragmatic vagueness is employed to adapt to various contextual factors. In this research, the adaptation is divided into self-directed adaptation and other-directed adaptation. If the contextual variables are related to the addresser, then the adaptation is viewed as being self-directed; if the contextual factors are connected with the hearer, the adaptation is regarded as being other-directed. The research findings indicate that pragmatic vagueness is used to adjust to social conventions, psychological motivations, and emotions if the adaptation is self-directed whilepresences in the speech situation and the addressee’s stereotyped expectation are the two kinds of contextual correlates in the other-directed adaptation. The scrutiny of the contextual correlates adapted by pragmatic vagueness enables us to draw the conclusion that the choice of pragmatic vagueness is, as a matter of fact, the result of linguistic adaptation.Having known how and why pragmatic vagueness is exploited in verbal interaction, we still feel curious about what functions or communicative effects pragmatic vagueness has or is intended to have. The present investigation finds out that pragmatic vagueness can enhance the flexibility of the utterance, improve the appropriateness of the utterance, and create special pragmatic effects. Besides, some specified sub-functions are also pointed out in the analyses.Pragmatic vagueness is a pervasive language phenomenon in our routine conversations. A dynamic and systematic research may prove both its theoretical and practical values in the linguistic circle.