Abstract: In Chinese,the separation of a splittable compound into two morphemes functioning just as syntactic elements poses a challenge to the"reification"approach of the mainstream formal linguistics.This paper analyzes the cognitive motivation of this syntactic phenomenon under the framework of the baseline/elaboration model proposed by cognitive grammar.It is proposed that the split structure is derived from the elaboration of the compound (i.e.the baseline) by the inserted construction.The elaboration as such consists in establishing the conceptual connection with one of the two morphemes,and thus leads to an increase in the prominence of the two morphemes and contributes to their further ionization.Besides,the novel split use of non-splittable words also involves the metonymic usage of one of their constituents.The analysis in this paper provides a natural explanation for the unidirectional predictability of the different split types as well as their diachronic gradualness,and it also provides a new perspective on the nature of the splittable compound.