Abstract: The aerodynamic derivatives were expressed by the fluctuation pressure on the plate surface through rational simplification. The influence of fluctuation pressure distribution characteristics on the aerodynamic derivatives was studied by using of numerical simulation method based on the fluid-solid loosely coupled calculation strategy and existing fluid software user defined function (UDF). The influence of aerodynamic derivatives on the model vibration and aerodynamic coupling phenomenon were explained at micro level. The study shows that aerodynamic coupling flutter derivative which produced different action on the flutter depended on the model surface fluctuating pressure distribution. So the main factor of model flutter was determined by the fluctuating pressure distribution. The main component of fluctuation pressure was drifted to the model windward side in the flutter critical state, which caused the center of torsional vibration move forward and not coincide with the geometric torsion level.