Aiming at the requirement of two-dimensional sub-micron precision synchronous measurement for ultra-precision motion stage, a reflective two-dimensional grating measurement system is proposed and established. The synchronous measurement method of plane displacement of reflective two-dimensional grating is investigated, and an error transfer model of reflective two-dimensional grating measurement system is established. Through Vold-Kalman filtering algorithm, the high-order harmonic error and amplitude/phase error in the grating signal are corrected and filtered in real time. An arc-tangent subdivision algorithm and period measurement method are used to measure the frequency of the orthogonal pulse of the grating to realize the high-resolution measurement and real-time speed measurement. A reflective two-dimensional grating measurement system with sub-micron measurement accuracy is constructed, in the measurement range of 500 mm×500 mm, the positioning accuracy of the x-direction and y-direction is ±0.3 μm and the resolution is 0.005 μm.