Abstract: Suspender is the major load-bearing component of a bridge and need to be regularly tested for cable force. This paper introduces a method based on the pyramidal Lucas-Kanade optical flow method, using Shi-Tomasi corner points as feature points. The principle of the method is explained, and the long, medium, and short tie rods of the Longchong Pedestrian Bridge in Dongguan were tested for cable force in a non-contact manner. The test results are compared with those obtained using traditional acceleration sensors to explore the reliability of the method and the impact of factors such as day and night, and with or without vibration, on the accuracy of cable force testing. The research results show that the cable force testing method in this paper can meet the measurement requirements of actual engineering and is suitable for both day and night, and has good engineering application value.