Since November 1978 Deng Xiao Ping has propelled the economic reform in Mainland China, then her defense spending grows continuously, the P.R.C.’s defense spending has broken through a hundred billion renminbis, we can not overlook its influence on Asia and the world. While the Mainland china grows the defense spending year by year, it lowers on R.O.C. on t e contrary, the situation makes the gap wider and wider. This study proposes the forecast model of Mainland China’s defense spending and estimates its amount to make our people realize its trend in the future, and study its real meaning to our national defense budget policy, the report may suggest the authorities distribute properly the defense resource.