Abstract: The contribution of more secondaries particles in the contributon Monte Carlo method by Dubi and Gerstl is negative^[3,10]. The negatively contributing particle often makes the statistical fluctuation, of the Monte Carlo estimate become large and the computation is more time-consuming. Therefore, if is Very necessary to solve the negatively contributing problem of the secondery particleIn this paper, a new contributon Monte Carlo method called the SCR qositi-ve contributon method is proposed. In any case, the SCR positive contributon method is surely betfer than the contribufon method by Dubi and Gerstl hence the former can replace the latter thorughly, too. The negativily contributing prob-lem of the secondary particle for tho source convex region is solved, The results of the practical calculation by examples indicates that the efficiency of the present method can be raised by 1.5 of 3.4 times in comparison with the method by Dubi and Gerstl.