The statistic meaning of the diffusivity function of Perona-Malik diffusion filter was analyzed.A statistic interpretation model was proposed that the diffusivity function defines a probability density function(PDF) for the edge estimator as a random variable.This model overcomes the difficulty of no unified theory of designing and selecting the diffusivity functions.A novel anisotropic diffusion filter based on this model was designed.Experiments demonstrate that the novel filter promises the same efficiency in images denoising as PM method,and with less recursion times.So our interpretation model of the diffusivity function provides an effectively method to custom anisotropic diffusion filter for special application.