Historically, shiyi (causative) verbs have grammaticalized into multiple syntactic functions, including causative, passive, conditional and concessive conditional ones. Focusing on the poly-grammaticalization of shiyi verbs, this paper aims to illustrate the different functions which the perspectives of syntax, semantics and pragmatics serve in unveiling the properties of grammaticalization. By looking at the aspect of syntax, it helps investigate the conditions for grammaticalization; from the perspective of semantics, it helps examine the direction of grammaticalization; finally, from the perspective of pragmatics, it helps analyze the subsequent development of each syntactic function. For each argument, empirical evidence will be provided from the poly-grammaticalization of shiyi verbs. In order to draw a complete picture, this paper also refers to the serial verb constructions, the causative disposals, etc.