Aiming at the problem of line collision accident of large cranes under transmission lines, a method based on object detection and binocular distance measurement is proposed to control the risk. Firstly, the proposed method uses YOLOv4 algorithm to detect the transmission lines. Then, considering that binocular cameras at different angles can lead to image brightness differences, A binocular ranging algorithm based on AD-Census cost SGBM (Semi-Global Block Matching) is proposed. Finally, the effectiveness of the proposed method is verified by experiments. The results show that the average confidence of the method can reach 81.67%, the measurement error can be controlled within 0.4 meters within 5~8 meters, and the average detection time is 50ms. Compared with the original binocular ranging algorithm, the measurement accuracy of the improved algorithm is improved to some extent. The proposed method can accurately measure the distance between the crane boom and the transmission line, which has certain significance to prevent the crane from hitting the line.