Smart contract is the prediction of blockchain describing the core logic of business scenarios. Contract credibility has become an important trend and inevitable choice in the development and application of blockchain technology, while contract credibility modeling has become a prerequisite and necessary means to construct a trusted blockchain. In order to explore and clarify the basic scientific problems of contract credibility and establish the theoretical basis of contract credibility measurement, we can explore the contract credibility and its evolution law by combining the basic ideas of dynamic system, study the dynamic mechanism of contract credibility evolution under various internal and external factors, and establish the corresponding dynamic model. Therefore, it can be considered that the credibility of smart contract system is the statistical property of the behavior of blockchain in dynamic open environment. Through modeling analysis, the correspondence between the limit evolution behavior of the contract trust attribute and the dynamic system characteristics can be explained, so as to interpret the dynamic characteristics and evolutionary complexity of intelligent contracts. On the other hand, we can use the dynamic statistical analysis method to give the invariant measure evaluation method of the contract credibility statistical index and the dynamic criterion of the contract untrustworthiness.