A method of calculating the grayscale similarity and structure similarity between two pictures is presented based on the image model and vision characteristic of human eye. The product of grayscale similarity and structure similarity is taken as the judging criterion of image quality based on the calculation of the grayscale similarity and structure similarity. The performance of soft morphological filtering method with different noise intensity and different configurable parameter is analyzed. The results of experiments show that the soft morphological filtering method could get the same effectiveness as the typical method in small module; and the soft morphological filtering method has better robustness after adjusting parameter in big module.