Gerchberg-Saxton (GS) phase retrieval iteration algorithm is widely used in multi-plane reconstruction despite of the low correlation coefficient C values of most planes. Method of compensation, which we call strong compensation, was proposed by the researchers but it has little function. In this paper, an improved algorithm based on the concept of weak compensation is proposed. Introduction of weight factors to adjust the balance of the multi-plane reconstruction and to realize the weak compensation is the core concept in this proposal. The simulation results show that with this method the average and variation of C values can be improved by at least 59.82% and 97.03% compared with original GS iterative algorithm, respectively.