In recent years,improving the photon absorption rate of infrared detectors is one of the key researches in infrared detection,among which increasing the transmittance of incident light is an important step.The application of traditional multilayer antireflective films is limited by adhesion,thermal mismatch and lack of stability.Photonic crystal is a kind of reflection improvement effect which can be achieved by machining microstructures directly on optical surface.It does not have such problems as above,and shows a good reflection improvement effect.However,the complex structure of the current photonic crystal design poses difficulties for process machining.Based on the above problems,several simple geometric structures of ZnS photonic crystal are designed in this paper,including cuboid,cylinder,hexagonal prism and pyramid structure.In the long wave infrared band of 8～10μm,the best average transmittance of each kind of photonic crystal structure is above 90%,and pyramid has the best anti reflection effect.The pyramid array structure is designed,and the transmission simulation results show that the pyramid array gap can maintain more than 98% transmission in a certain range.Finally,the influence of the thickness and temperature of different substrate materials on the transmission of photonic crystal is investigated.The research in this paper can provide some reference for the research of photonic crystal anti reflection and the design of micro and nano optical devices.