This paper presents a novel grating moving light modulator based on Micro Optical Electromechanical System(MOEMS) technology and introduces its structure,operation principle and fabrication process.The device can be used in projection display etc.The relationship between optical characteristics and geometrical parameters of this device is established through optical analysis,optimization and simulation,and the ±1^st order diffraction efficiency η and contrast V are theoretically 37.0% and 625 respectively for e=0.5,d=6 μm,L=39 μm,w=36 μm,w₀=1.5 μm and e,d,L,w and w₀ are occupation ratio,grating constant,length,width and margin of the movable grating respectively,the gap between the movable grating and the underlying reflector are 0.65 μm and 0.78 μm respectively in on and off states,and the single pixel size of the device is 51 μm×51 μm.