Posterior-Mean Rectified Flow (PMRF) is an innovative image restoration algorithm that minimizes mean square error (MSE) while ensuring the realism of images by optimizing posterior mean predictions and the rectified flow model. The PMRF algorithm is both simple and efficient, theoretically grounded in optimizing posterior mean predictions (minimum mean square error estimates) to match the true image distribution. It excels in image restoration tasks, effectively tackling various degradation issues such as noise and blurring, while providing good perceptual quality.