Abstract: From the perspective of cognitive construction grammar, constructions are regarded as basic symbolic units and the syntactic and semantic relations of their internal components form a symbolic link relationship based on specific meanings or functions. It shows that the overall semantics of a construction is generated by the understanding of the cognitive context in specific use, and mapping is the realization mechanism of the internal syntactic semantic symbolic link relationship in use. People's cognitive ability drives them to form multiple mapping mechanism based on different aspects of the construction highlighted by mapping, such as functional mapping, cognitive node collocation mapping and semantic extension mapping. The syntactic semantic symbolic link mapping mechanism of constructions plays a key role in dominating the overall semantics of constructions.