A modified power inversion algorithm for anti-jamming satellite navigation is proposed in this paper. First, the main factor that degraded the performance in feebleness jamming environment is abstracted by theoretical analyzing. Then, taking out the eigenvectors corresponding to the feebleness jamming form the power inversion optimum weights and the normalized eigenvectors corresponding to the noise is used as the optimum power inversion weights vectors. Strong and feebleness jamming signals could be degraded by using the method proposed in this paper. The computer simulation results verify the effectiveness of the method in this paper.