In order to further improve and mend the engagement characteristics of heavy duty wet clutch during the using process,the model of the engagement characteristics of heavy duty wet clutch is established by combining the fractal geometry theory.Finally,the micro convex body of the contact area,fractal dimension and contour amplitude scaling factor of the friction pair in the wet clutch contact region engagement friction force influence law and the change law of wet clutch friction temperature rise are obtained through theory and test bench method.The research results show that without considering the effect of the micro convex body,with the increase of the fractal dimension and the actual contact area,the wet clutch friction force will increase; with considering the effect of the micro convex body,with the increase of the fractal dimension and the actual contact area,the wet clutch friction force will decrease; with the decrease of the contour amplitude scaling factor,the friction force and the maximum temperature rise can be increase; the results show that the theoretical calculation between the fractal theory results and the experimental results are basically the same.