Abstract: In order to remove noise effectively and preserve key details,a more effective and adaptive diffusion denosing model was proposed．A new diffusion function was built based on the P-M model．The new diffusion function would be a constant when the gradient is low．After the gradient exceeds a certain threshold,the new diffusion function becomes a monotone descending function which reduces to zero at a certain gradient．The characteristic of the diffusion function makes the improved model smoothing faster in homogeneous area and stop in edge．The experiment results show that the performance of the improved model is better than the traditional methods.

Key words: Image processing,Image smoothing,Anisotropic diffusion model,Diffusion function