Aeroengine blades bear the common act of thermal load, centrifugal load and aerodynamic load under conditions of working. These loads will not only change the mechanical performances of the blade material, but also make the natural frequency and mode shapes of the blade different from the stationary ones at room temperature. All the factors are considered accurately by using finite elements analysis (FEA) software ANSYS during modal analysis. The working temperature of blades is obtained from thermal analysis first, and then is coupled to structure elements to calculate the thermal stress of the blade by using structural analysis. After obtaining the thermal stress, the FEA is restarted by applying centrifugal load and aerodynamic load to study multiple stresses of the blade. At last, taking the multiple stresses as prestressing force, natural frequency and mode shapes of the blade are analyzed under conditions of working. The paper synthesizes both temperature and stress influence on blade modal, and a modal analysis method of aeroengine blade is obtained based on thermalstructure coupling prestressing force. And this method has an important theoretical meaning and engineering practical value.