Binocular ranging technology is an important branch in the field of machine vision. The use of binocular ranging technology on the high-voltage transmission line inspection robot provides a powerful guarantee for the robot"s online obstacle location and obstacle crossing. In order to realize the real-time and reliability of the on-line ranging of the inspection robot, this paper improves the traditional ranging algorithm and proposes a binocular real-time ranging algorithm for the visual navigation of the high-voltage transmission line inspection robot. The left and right cameras cooperate with each other. On the basis of the recognition of the left camera obstacle, the line obstacle is preset to take a point, and then the distance is taken by the two cameras, and the distance of the obstacle to the lens is continuously updated as the robot advances. The experimental results show that the ranging algorithm has the advantages of high speed, high precision and strong real-time performance.