The algorithm for automatic crack detection and identification in slab track images is designedbased on digital image processing technology and many procedures such as image auto-segmentation, edge extrac.tion, edge removing of slab track structure and false crack identification. The algorithm has been proved accuratelyin extracting and marking the crack region by applying to slab track images from actual acquisition. In the experi.ment of 1000 images, all the six manually detected crack images are also detected automatically by the algorithm, i.e., the accuracy rate is 100%. The computational speed of the algorithm can satisfy the real-time detection require. ments.