The photoelectric currnt and convert efficiency have been calculated for the polycrystalline CdS/CuInSe2 heterojunction solar cell using A. Rothwarf's grain boundary recombination lose model, in which the internal recombination factor G and the potential barrier width of the heterofunction are considered. The analytic show that the doping concentrition NA has a best value, and the calculated conclusion is very close to the reported experimental value of L. L. Kazmerski.