Focusing on the problem that the GPS signal is susceptible to interference, an adaptive anti-jamming algorithm based on FCGA（Floating point number Coded Genetic Algorithm）is presented. First, according to the analysis of the output signal of the adaptive array, the relation formula between the radiation pattern of the adaptive array and the weighted vectors is induced. Then, the objective function with constraint conditions is obtained by LCMV criteria（Linear Constrained Minimum Variance criteria）and optimized by using the FCGA. Finally, the simulation experiment of 22-unit uniform circular array is carried out for its radiation pattern and output SINR. The results show that, by using this method, the main beam can be kept in the directions of the desired signal, and simultaneously the hollow beam is formed in the directions of the interference signal. Thus, the output SINR is not depressed, but kept constant. The goal of interference cancellation is achieved.