The invention discloses a numerical control machine tool profile error three-dimensional measuring method based on monocular vision, belongs to the technical field of computer visual measurement, andrelates to the numerical control machine tool profile error three-dimensional measuring method based on monocular vision. In the method, firstly, a monocular camera is mounted on a measuring system mounting frame, and is positioned on the inclined upper side of a machine tool worktable. A Zhengyou Zhang calibration method and a high-precision checkerboard calibration board are combined to calibrate inner parameters and distortion parameters of the monocular camera. A measuring reference is mounted after calibration to drive operation of a machine tool to generate a dynamic trajectory; meanwhile, the monocular camera is triggered to shoot motion sequence images of four encoding points on the measuring reference; an iterative algorithm is used for data processing of each image frame to calculate space coordinates of a reference point; and after traversal of each image frame by a processing algorithm, the reference point is connected to obtain a machine tool motion trajectory under a camera coordinate system. Then, the trajectory is projected under the machine tool coordinate system to compare with a theoretical trajectory to obtain machine tool profile three-dimensional errors. The method is simple in operation and excellent in measuring stability.