1. An image interpolation method for using a probabilistic neural network model to perform an adaptive interpolation on an interpolation point of an image, the image interpolation method comprising steps of: (1) selecting plural reference points neighboring the interpolation point; (2) obtaining an anisotropic Gaussian function value of each reference point of the plural reference points according to an edge direction angle, a horizontal smoothing parameter, a vertical smoothing parameter and a distance between each reference point and the interpolation point; and (3) performing a statistics method to integrate and compute the anisotropic Gaussian function values of the plural reference points, thereby obtaining an interpolation value of the interpolation point.