As a branch of augmented reality technology, 3D laser projection positioning technology can accurately present the contour information of the digital 3D model of the product and part of the manufacturing information at the required place on the product assembly site. The 2D galvanometer system is an optical reflection system that can precisely control the optical path of the laser beam. The calibration technology of the 2D galvanometer is the key to achieving high-precision 3D laser projection. As the application of two-dimensional scanning galvanometers expands from two-dimensional plane scanning to three-dimensional space scanning, the difficulty of galvanometer system calibration is also increasing, and the continuous expansion of galvanometer system applications promotes the development of galvanometer system calibration technology. However, the calibration process of the existing laser projection technology has the problems of complicated process operation, low efficiency and the need to use high-cost equipment such as laser trackers, resulting in the inability of 3D laser projection to be widely used in the field of view of assembly manufacturing. Vision measurement technology is a typical non-contact auxiliary measurement technologies with high measurement accuracy. It can not only collect a large amount of high-precision data for the calibration of the galvanometer, but also can be used as a basic coordinate system to realize the alignment of the coordinate system of the projected object and the galvanometer coordinate system. In addition, visual measurement has the advantages of mature development and low hardware requirements. The study of the 3D laser projection system based on visual assistance can lower the threshold for the realization of this technology and promote the promotion and application of 3D laser projection. Aiming at the problems of complicated operation and low efficiency in the existing 3D laser projection system calibration, a 3D laser projection calibration method based on a homography matrix is proposed. Firstly, the monocular vision was introduced as an auxiliary means to establish a model of the 3D laser projection system; secondly, the pose of the projected target was solved by using the 2D homography of the image, and the conversion relationship between the galvanometer and the camera was calibrated. The performance of the proposed calibration method is analyzed from three angles of error, stability and error distribution, and the reliability of the 3D laser projection calibration method based on the homography matrix is verified. By independently building a 3D laser projection system based on visual aids, and conducting specific experiments with standard parts as the projected parts, it is proved that the proposed calibration method can solve the above problems. The experimental results show that when the distance between the projected part and the galvanometer is within 3 m, the calibration time is less than 5 min, and the projection accuracy can reach 0.3 mm. The calibration method of the homography matrix is limited to the plane object, and it is suitable for the case where the projected part is a plane. Compared with the domestic conventional calibration method, the method in this paper avoids the complicated pre-calibration process and improves the calibration efficiency. Such a positioning device reduces the cost and solves the problem of low operation efficiency of the entire 3D laser projection system at present.