The objective of the invention is to solve the technical problems of low precision and low resolution of an existing dynamic optical wavefront phase measurement device. The invention provides a dynamic high-resolution optical wavefront phase measuring device and a measuring method, and the device and the method can achieve the active optical testing of the surface shape of an optical element and the wave aberration of an optical system through a laser, a collimating mirror, a plane mirror, a spectroscope, an absorber, a mixed modulation grating, a detector, a computer, different F # standard lenses, and a calibration mirror. The resolution is determined by the size of a detector pixel, high-resolution optical wavefront phase measurement can be achieved, and the resolution can be smaller than 0.01 mm. According to the method, a system background error is used as system data after being calibrated once, and the measured surface topography information can be calculated only by collectingan image once during actual surface shape measurement, so that compared with the traditional phase shift interference method, the method is not influenced by environments.