To improve the compatibility between wood and polypropylene, a compatibilizer was prepared with maleic anhydride grafted polypropylene under γ-rays irradiation. The boards of wood/plastic composites were made by a twin screw extruder after mixing the compatibilizer with the dried and sieved wood powders. The observation by use of scanning electron microscope demonstrated that the compatibility between wood and polypropylene matrix was obviously improved while the mechanical properties including flexural strength, tensile strength and impact strength of such boards were greatly enhanced. And the optimum mass fraction of addition agent was 4% in the process of pre-irradiation grafting.