4f system has the characters of noise and low-pass.In order to remove the image noise and to protect the image texture of its outputs,an image denoising method based on Nonsubsampled Contourlet Transform(NSCT) is proposed combined with the continuity of image texture.Based on the classic hard threshold denoise method in NSCT domain, it adopts a smaller threshold to remove the small amplitude noise to protect the image detail better and protrude the remanent big amplitude noise, then uses the continuity of image texture to remove the large amplitude isolated noise from the consecutive image detail in the high-frequency sub-band images.Eventually the noise is removed and the image detail is protected in the same time.Experiments show that the method can reach the same denoising and can better protect image details for that its Peak Signal Noise Ratio(PSNR) and Structure Similarity(SSIM) have been improved by 0.5~1 dB and 3%~5% respectively as compared with those of traditional methods.