According to the characteristics of coal cutting drum of shearer,the stress of drum is analyzed,the mechanical model of planetary reduction gear solar wheel’ s torque,instantaneous rotational speed and tangential force are obtained.By using the MATLAB software,the simulation of the derived mathematical model in sun wheel is carried out,with the pick position angle changes,the variation images of the solar wheel’s torque,instantaneous rotational speed and tangential force are obtained.Finally,the damage value under different loads is obtained by experiment,and based on the application of the Miner’s linear cumulative damage,the life of sun wheel is analyzed,it reaches a conclusion.For further optimal design of small size,high power of shearer provide a reliable theoretical basis.