A modulation microscopy system for specular surfaces is proposed. The system includes two telecentric lenses, a transflective lenses, a microscope objective, a CCD camera and a DMD digital projector. The fringe image generated by the digital projector is imaged by the telecentric lens and the microscope objective to the object surface of the microscope to obtain a virtual standard fringe pattern. The reflected image of the virtual fringe surface to be tested will return along the optical axis of the microscope objective. Entering the CCD image plane, the object to be measured moves along the optical axis under the control of a high-precision one-dimensional translation stage. According to the phase shift algorithm, the modulation image of each position can be calculated from the acquired fringe pattern, and the maximum modulation curve is found. The corresponding position can complete the three-dimensional shape measurement of the object to be tested. The experimental results show that the micro-modulation measurement method can obtain high-precision surface shape, and is especially suitable for surface shape measurement of objects with drastic changes in micro-morphology.