Abstract: The thinning of the binary image has important application in target recognition.Zhang's fast parallel thinning algorithm is a kind of common thinning algorithm.Its thinning result maintains the connection of the original image,has a good structural form and has no burs.However it can't ensure the single pixel width,which brings difficulties for post-processing.In this paper,we make some improvement about Zhang's fast parallel thinning algorithm.Experimental results show that the results of the improved algorithm can not only ensure a single pixel width,but maintain the advantages of the original algorithm.