Median filter can inhibit the impulse noise in the image, butit always erodes or dilates the edges of images. H.S.Ranganath mentioned that impulse noise could beremoved through modifying the intensity of those contaminated pixels step by step using PCNN. Obviously this method consumes much more time in computation. Combining the PCNN model with the median filter, this paper presents an impulse noise filter based on a simplified PCNN model which has less parameters. Not only can it remove the impulse noise effectively, but also it keeps the details of images as can as possible. It can be verified through experiments and theory analysis that this kind of filter is superior to the normal median filter and the filter mentioned by H.S.Ranganath, no matter in the aspect of noise removal or in the aspect of keeping details.