In order to study the strength of the rotary ear frame of the roadheader, a multi-rigid-body dynamic model of the assembly of the rotary ear frame and the cutting part in the roadheader is established based on ADAMS, and the dynamic characteristics of rotary ear frame is analyzed during the movement of the lifting cylinder under punching process. Through the analysis, it is concluded that the strength of rotary ear frame is weak, so the optimization of it is needed. The dynamics analysis of the new model is carried out again. And it is concluded that the force of the new rotary ear frame is reduced and it meets the design requirements.