In the existing biomass briquette production market, the screw extrusion-type machines are applied at the earliest. However, the shortcoming of the easily-worn screw head limits their application and large-scale development. In this paper, the main reason of the impact on screw life can be identified by the force and motion analysis of molding biomass. Therefore, theoretical basis for the improvement and optimized design of the molding machine can be provided. Furthermore, new paths which can increase the machine efficiency, reduce production costs and increase biomass briquette production can be found.