In order to study the mechanism of fatigue failure of harmonic reducer flexspline,by using ANSYS n Code Design Life 15. 0 software,the fatigue analysis of flexspline is carried out based on the results of finite element analysis. Comparing the analysis results with the engineering fatigue damage of flexspline,it is found that tooth circle and the bottom of the flange are much easier for fatigue failure,a basis for the design of flexspline is provided.