In 3D projecting grating profilometry, we are often persecuted by some disgusted phenomenon of images, such as reflecting flare, overlapping of grating and other noise. All these can bring a bigger error in image processing. The intention of this paper is to propose some special filter and other methods of image processing. The technique we applied is based on peculiarity of projecting grating profilometry image, which has obvious directionality. We used the nonsymmetrical multi band-pass filters to reject the high frequency noise along the grating and other component except base frequency part. The result obtained from the processed image by multi band-pass filter is much better than that from primary image. The method is propitious to measure some smooth surfaces.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.