Abstract:Reason event thematic role, which is the cause of action or situation, has three features:[+event],[+be already so] and[±Main body sharing]; it is usually marked by the prepositions: yin (wei), you (yu) and wei (le), which differ in marking subjective and objective causes . It is this difference that checks the exchange between them. There are two different types of containing sentences of reason event prepositional phrases: direct reference reason and indirect reference reason, both of which are generated by the combination and transformation of the two syntactic expressions of reason event and its resulted event.