Due to influences of installation error of rudder and wing, engine thrust misalignment and random disturbance, conical motion with large amplitude and divergence may occur to rocket projectile, which causes test failure. In this paper, mechanism of conical motion was analyzed. When longitudinal and transverse movement frequencies close or cross and amplitude of missile body is larger, the conical motion divergence is presented. Simulation results show that through mathematical simulation of longitudinal and transverse movement frequencies and oscillation amplitude of rocket projectile, the control requirements of wing surface mounting error and engine thrust misalignment are given.