ing at the problems that the measurement range of a monocular light pen three-dimensional measurement system is small and this system can not realize the full space measurement, a full space light pen monocular vision measurement method based on precision rotary platform is proposed. First, the camera is fixed on the precision rotary platform, and the calibration plate is photographed at different angles to obtain the position of the camera optical center in the calibration plate coordinate system under different angles. Second, through the plane fitting of principal component analysis (PCA), the plane where the camera optical center is located and the rotation axis direction vector of the camera rotation motion are obtained, and the position of the camera rotation axis is obtained by using the spatial least square circle fitting. Third, with the help of the precision rotary platform reading and Rodriguez formula, the rotation angle of the turntable is transformed into the rotation matrix and translation vector of the camera. Finally, the measurement data of the camera at different positions after rotating a certain angle are converted to the same rotary platform coordinate system by using the calculated transformation matrix to realize the full space measurement. Experimental results show that in the measuring system using the same light pen, the measurement method in this paper can almost achieve the same precision as that of the traditional monocular vision light pen measurement system, achieve 360° full space measurement, and greatly expand the scope of applications of the monocular light pen.