It is difficult to realize the STOL and high-speed cruise at one time when designing an aircraft, whereas the application of power-lift technology has successfully solved this technical problem. The research about the dynamic characteristics of power-lift aircraft in hover and low speed flight regime is key important for the selection of control strategy in transition process. However, if adopting the traditional aerodynamic calculation method based on thrust coefficient concept, the hover and low speed forward flight of power-lift aircraft cannot be studied as a unified process and the stability derivatives cannot be accurately calculated in low speed. In this paper, a method for calculating the stability derivatives and model the aircraft by using full dimensional aerodynamic data is proposed, which can not only solve the problems mentioned above, and it is very convenient for the design of the control law in the transient process.