The invention relates to application of 4, 4-diphenylmethane-bis (methyl) carbamates (DPMC) extracted and isolated from Cortex Mori and preparation of medicine for diabetic nephropathy. The pharmaceutical composition is made up of DPMC as active ingredient and the normal drug carriers, and the weight percentage of active ingredient is 0.1-99.5%. For the remarkable effect of prevention and cure for diabetic nephropathy and convenience for use, it will be a new facultative drug for patients.