Based on the analysis on the force and movement of biomass materials extruded by screw molding machine, disassembling the whole screw into the screw head and the main screw body, the molding sleeve into forming looper and Paul-type sleeve, and optimal design of the parameter of screw head which contains spiral leaves diameter D, blade pitch S, screw shaft diameter d, and the sleeve data was carried out. The tests showed that changing the screw head and forming looper was able to reduce the wear, the service life of the screw head and the main screw body was up to 90h and 1000h respectively, biomass briquette production was increased, production efficiency compared with the original machine increased 66.12kg / h. The optimal design promoted the applications of biomass briquetting machine.