In order to examine the behavior of planetary traction drive when the loading torque varies rapidly, experiments were performed. From the experiments and discussions, following conclusions were obtained. (1) Because of the higher contact pressure between rollers, slip ratio between ring roller and planetary roller increase first when the loading torque is over the transmissible torque of the planetary traction drive. (2) If the slip ratio between ring and planetary roller became high, traction coefficient between ring and planetary roller increased and slip occurred between sun roller and planetary roller. At last severe wear and siezure occurred. (3) If the temperature of the surface of roller reached about 160°C by frictional heating, traction coefficient started increasing. Similar phenomenon was found in the four ball test using hot traction oil.