Abstract: The recognition of tokens is an indispensable procedure in appraisal analysis. The linguistic mechanisms of implicit appraisal proposed by researchers at home and abroad have helped to address the issue to a certain extent. However， there is still a lack of connection between the varying mechanisms， which results in the limited explanatory power to some evaluative phenomena. The Semantic Field Theory and Systemic Functional Grammar are drawn on to reveal the underlying commonality of the evaluative mechanisms put forward by James Martin and other scholars， and then it is proposed that semantic relations are the basis of linguistic mechanisms for implicit appraisal. Based on this observation， some other linguistic mechanisms， such as mismatching of semantic relations， presumption of responsibility and logical derivation， are discussed. Furthermore， semantic relations are explored in respect of their selection framed by the context.

Key words: implicit appraisal, semantic relation, linguistic mechanism, context