Abstract: The real-time monitoring of cracks is important for concrete facilities. Automatic detection technology based on digital image has been widely used in highway, tunnel and bridge crack detection because of its advantages, such as rapidity, accuracy, intelligence, etc. The research status of three kinds of concrete cracks' detection methods are analyzed and summarized comprehensively from two aspects of hardware and software. It is pointed out that the current detection methods are insufficient, such as system integrity, generality, precision. So a set of more efficient, more stable and smarter crack auto-detection system needs to be developed urgently, which will be one of research directions of concrete crack detection.