To deal with low-contrast and high-noisy natural images, an image enhancement method based on internal generative mechanism (IGM) and improved pulse coupled neural network (PCNN) is proposed. First, the original image is decomposed into rough sub-graph and detail sub-graph by the theory of IGM. And then, an im-proved PCNN method is adopted to make the rough sub-graph more clearly. At the same time, the enhancement method which PCNN incorporates with fuzzy sets is introduced for the detail sub-graph so as to sharpen the im-age edge and remove outliers. Finally, the final image is reconstructed by processed rough sub-graph and detail sub-graph. Experimental results show that the proposed algorithm can effectively enhance the image contrast and image contour, as well as filter out some noise without any loss of image edges.