In the automatic cleaning process of embedded aeronautical ground lights in airport, in order to obtain the center of lamps emitting port and the relative position of the manipulator to achieve precise positioning of the manipulator, a positioning system of lamps cleaning for manipulator arm based on monocular vision is designed. Firstly, the kinematics model of the manipulator was established by D-H method. Then, according to the strong backlight characteristics of lamps and environmental interference at night, an improved Otsu algorithm was proposed to segment the image by optimizing the threshold criterion and reducing the search range of threshold, and then the center of mass method was used to extract the center position of the lamps emitting port. Finally, under night conditions, the experiment was analyzed and the least square method was used to compensate the positioning error. The experimental results show that the designed manipulator arm positioning system of lamps cleaning has high speed and high precision. Compared with the traditional Otsu algorithm and the improved random Hough transform algorithm, the positioning accuracy was improved by 72. 5% and 55. 5% respectively, and the average positioning accuracy reaches 8. 7 mm, which meets the requirements of lamp cleaning.