With the development of Electronic Commerce,both consumers and merchants on Internet are more and more concerning about the trust.The trust of Electronic Commerce has been studied deeply by many foreign scholars.As a new research field,it needs a basis of some theories.This paper introduced twelve theories,including theory of planned behavior,technology acceptance model,transaction cost economics,incomplete contract theory,and so on.On the basis of the introduction,the twelve theories were summarized.At last,a theoretical framework for the research was given.