Abstract: In order to study the through-flow characteristics of planetary transmission mechanism under high-speed working conditions, a dynamic-static coupling multi-stage planetary transmission rotating oil passage oil-air two-phase flow field simulation model was established, and the variation law of two-phase flow field in rotating oil passage at different speeds was analyzed. A visual test bench for the flow field of the rotating oil passage was built, the flow distribution test was carried out, and the oil-air two-phase distribution of the rotating oil passage was obtained. Research results indicate that the inlet flow rate first increased and then decreased with the increase of rotational speed. At low rotational speeds, the rotating oil passage was filled with oil, and the outlet flow rate of the rotating and stationary planetary gear set were similar. As the speed increased, air appeared in the rotating oil passage, and the higher the speed, the higher the air content. The flow rate of the rotary planetary increased first and then decreased, and the static planetary decreased and then increased. When the input speed reached 12000 r/min, compared with the static condition, the outlet flow rate of the rotating planetary gear set 2 and the stationary planetary gear set increased by 12.5% and 60.1% respectively, and the rotating planetary gear set 1 decreased by 61.6%. The test results of the outlet flow of the dynamic-static rotating oil passage have the same variation law as the simulation results. A large amount of air appears in the rotating oil passage under high-speed conditions, which is consistent with the simulation results and verifies the accuracy of the simulation model.