The invention provides a single-probe optical curved surface on-machine measurement method facing precision and ultra-precision machine tools, belonging to the technical field of optical curved surface measurement. The invention aims to solve the problem that a conventional error separation measurement method has a large sampling interval and is not suitable for an optical surface with an undulating surface. The method is realized through a linear slide platform and a displacement sensor, thus the linear slide platform is fixed at the position of a Z-axis guide rail direction, the optical curved surface installed on a machine tool spindle moves along the Z-axis guide rail direction, in the movement process of the optical curved surface, optical curved surface patterns are measured through the displacement sensor along the Z-axis guide rail direction, the measured N optical curved surface pattern measurement data are separated by using an error separation method, and the real surface shape error of the optical curved surface and the straightness error of the machine tool are obtained. The method is used for the optical curved surface on-machine measurement with a large undulating surface.