In this paper, we propose an iterative focusing method based on a weighted Gerchberg-Saxton (GSW) algorithm using an optical transmission matrix. The process of solving the modulation phase by using the transfer matrix is abstracted as a phase recovery problem, and the transmission matrix and mean square optimization operator are used as transformation operators of the scattering system to iteratively optimize the modulation phase. Simulations and experiments confirm that the proposed method has a more significant multi-point focusing effect than the phase conjugation method and the mean square optimization operator. The proposed method provides a new idea for light field energy regulation.