In order to solve the interference between the rigid wheel and the flexible wheel tooth profile caused by the theoretical value of the cam radial deformation is inconsistent with the reality in the harmonic drive， taking the double arc harmonic gear without common tangent as research object, based on the improved kinematics method，the harmonic gear finite element model is established in ABAQUS. The maximum radial displacement of the long and short axes of the flexible wheel is extracted. Combined with the principle of double arc profile modification，the simulation analysis is carried out by MATLAB to study the influence of different cam radial deformation on the modification of the flexible wheel. The results show that with the increase of the radial deformation of the cam， the amount of tooth modification of the front end of the flexible wheel increases sharply，and the amount of tooth modification of the rear wheel teeth decreases slowly. When the radial deformation of the cam is about 0.49 mm， no interference engagement under no-load can be achieved after the modification. The finite element method further improves the principle of harmonic drive tooth profile modification.