1. A method for reducing spatial noise of images, the method comprising: obtaining a target pixel and building an operating block accordingly; operating pixel values of the target pixel and a plurality of neighboring pixels in the operating block to obtain a variance corresponding to the operating block; judging whether the target pixel is characteristic according to the variance; filtering the pixels in the operating block to obtain a modulated pixel value if the target pixel is not characteristic; and updating the pixel value of the target pixel to the modulated pixel value.