Questions connected with the determination of the dynamic loads arising in the mobile components of a planetary mill with a gear drive are considered. The influence of the structural and technological parameters on the magnitude of the loads is analyzed. A horizontal planetary mill with external (respectively, internal) spinning of the grinding drums was selected to conduct the study. Inertial forces that exert a significant influence on the motion were determined in the course of a power calculation of the planetary mill drive. Kinetostatics equations based on the d’Alembert principle were compiled. The angular velocity of the pinion carrier, the relationship between the geometrical parameters and the degree of loading of the drums were varied in the calculations. It was found that the support reaction and the circumferential force both vary according to the law of cosines over a narrow range. A method of calculating the dynamic loads on the support nodes of a planetary mill that takes into account the effect of the maximum number of parameters is developed.