Operations such as application and services are the basis of daily work on computers, safe and reliable application is an important goal of modern research on information security. In this passage, we build trust transfer model based on existing ideas of trusted computing. We guarantee application's static trust by ensure the integrity of application's dynamic library, we guarantee dynamic trust by building transfer model of the trust chain and by analyzing interactions between different applications, hence, the overall trust of application is ensured. Based on the idea of finite state machine and noninterference theory, we abstract computer system into applications, actions and different output states. We define dynamic trust by using mathematical language, provide prerequisites and properties of dynamic trust, deduce theorem of dynamic trust of application and demonstrate the theorem in our model.