The G-S hologram can be used to design spatial optical filter. Due to the refractive index difference between the medium and air, the phase of spatial light will change when it passes through the holographic plate. Based on the height modulation phase of each pixel photoresist, a 2.5D gray-scale holographic spatial optical filter was designed. The photoresists with different heights were prepared by gray-scale electron beam lithography, and the patterns were etched onto the silicon wafer by dry etching. The electron beam lithography process, development parameters and etching process were optimized. The high diffraction efficiency spatial optical filter was fabricated and characterized.