The photon propagation in media volume has been successfully simulated by a Monte-Carlo method, and a genetic algorithm is applied to overcome the difficulties in the research of inverse problem by traditional optimizations and search algorithms casued by the discrete and statistic results of the Monte Carlo simulation. The reconstuction for a single optical parameter of a scatter media model and the simultaneous reconstructions for multiple parameters of model are realized well by the Genetic Algorithm and a detailed explanation of its mechanaism in reconstructing is presented.