An analytical model for NGW planetary gear train with unequal modulus and pressure angles was presented in the dynamic way. In consideration of the eccentric error and tooth-frequency error of parts, the dynamic equation of each planet was found by using the theory of equivalent mesh error and the principle of dynamic equilibrium. After equation being solved, the load sharing characteristics was compared with the normal gear transmission. The load sharing behaviors were analyzed and compared by the values of the sun and the ring pressure angles, the difference of the gear error. The analysis results indicates that planetary gear train which is designed by the suitable pressure angles can improve the load sharing behavior, the floating sun-gear can make it better too, and the rotating speed influences the load sharing greatly, a better load sharing effect can be achieved for theirs unequal modulus and pressure angles under the same rotating speed.