In order to obtain the reliable theoretical basics to design inner gearing biomass ring briquetting molding, a mathematical geometric model of the punch, as key part of the molding machine was established. The method of combining both mechanical model building and finite element simulation analysis was done to analyze force state at meshing time of the punch and female die. And the Simulink module function of Solidwork was used to simulate meshing force state of the punch. The distribution law of the internal stress, strain and displacement of the punch was obtained, and the stress concentrated parts of the punch were found out. Simultaneously, the distribution law of internal stress, strain and displacement on the punch was obtained, while its temperature was risen to 300 益. The results showed that the punch endured force within allowable stress range, and showed that the inner gearing ring mold structure was reasonably, which met requirements of materials molding, ensured the molding life and reduced production costs.