In the planetary gear, the inequality of load distribution arises on each planet gear because of random errors of manufacture and assembly. This phenomenon results in an increase of load to each part, the occurrence of vibration, and a drop in efficiency of planetary gear systems. Though there are a number of studies which are connected with load distribution, many of them are static studies. However, in fact, the dynamic behavior of load distribution in driving is complicated because of the influence of the deformation in each part, dynamic characteristic of the system. Therefore, to explain these relations, a systematic experimental work was carried out using Stoekicht planetary gear(Type 2K-H) with spur gears. Consequently, the following items are explained in this paper : (i) The mean values of load distribution among the planetary gears are nearly equality, but variations of dynamic tooth loads grow large in the high-speed range. (ii) Even if load distribution is equality, it happens that gear tooth dynamic loads largely.