The dynamic load sharing characteristic of the 2K-H-type planetary gear system with floating center gear is researched in consideration of the manufacturing errors, assembly errors, time-varying mesh stiffness. The nonlinear dynamic model is set up and solved by using Newmark’s method. Then the time history of load sharing factor of the system with load balancing mechanism are obtained, and the effects of the floating clearance， the load torque, and the way of planetary gears assembled on load sharing factor are researched. The sensitivity analysis of load sharing factor is done by using finite differential method. The study provides useful theoretical guideline to the design of planetary gear system.