A blind navigation aid system was designed to improve the poor detection, complex structure and inconvenient to carry for the existing guide equipment. The system could detect all the obstacles between the ground and the user's head, and could deliver accurately the traffic information through a voice prompt to the user, so as to complete the navigation. The depth image rotation algorithm and detection obstacle technology were applied in this system to identify three types of obstacles including ground obstacles, ground pits and hanging obstacles. Meanwhile, the depth image filtering algorithm and obstacle distance calculation were used to determine the position of the obstacle in an effective range. A prototype was developed, and the experiments on the obstacle recognition and obstacle position detection were carried out in various scenes at a laboratory. The experimental results show that the navigation system can accurately identify the obstacle with an area more than 10-3 m2 and the holes with a height difference more than 0.02 m and can determine the best way to avoid the obstacle in an effective range by voice prompt to the user, so as to meet the daily demand to blind navigation. The development of this system and the applications of various algorithms not only have important effect on the blind navigation, but also have reference significance for the robot walking dependently.