This paper presents noise removal algorithm for gray scale images corrupted ..This paper presents noise removal algorithm for gray scale images corrupted by additive Gaussian noise. A robust open close sequence filter based on mathematical morphology for high probability additive Gaussian noise removal is discussed. First, an additive Gaussian noise detector using mathematical residues is to identify pixels that are contaminated by the additive Gaussian noise. Then the image is restored using specialized open-close sequence algorithms that apply only to the noisy pixels. Finally, black and white blocks that degrade the quality of the image will be recovered by a block smart erase method. Simulation and experimental results demonstrate that the robust open close sequence filter outperforms a number of other existing algorithms and is particularly effective for highly corrupted images.