Abstract: Methods of displacement measurement based on grating interFerometry, including classical dual-grating measurement systems,nonsymmetrical doubly blazed reference grating measurement systems,single grating measurement systems,grating measurement systems based on the 2nd harmonic Moiré fringes, concentric-circle grating two-dimension displacement measurement systems,and the two-dimension grating measurement systems, were introduced. The key problems and disadvantages of each system were presented as well. According to dual-frequency laser interferometer the dual-wavelength single grating nanometer displacement measurement was put forth based on the single grating measurement system.After analyzing its characteristics,it was pointed out that it could realize the measurement with a wide range,nanometer precision and nanometer resolution. After a general comparison among these methods,a conclusion of key technologies was drawn,and an outlook of displacement measurement based on grating interferometry was presented.