Abstract: The weighted function moments method is one of the principal methods to estimate the parameters of P-Ⅲ distribution in China, but it can only be applied in simple hydrological series. The formulae of parameters with historical flood series of above method have been derived in the paper. Based upon the Monte-Carlo experiments the results of the unbiasness and efficiency of the parameters and design flood values show that above formulae are effective, so the applied scope of weighted function moments method is expanded in the paper.