The infrared crystal ZnS bulk materials were prepared by chemical vapor deposition.The phase structure of ZnS was respectively analyzed with XRD and TEM, and their infrared transmittance was measured using IR.The results are as follows.The phase structure of ZnS deposited at temperature range from 550℃ to 700℃ and H₂S/Zn mole flow ratio 0.5～20 is mainly sphalerite, and there exited a few wurtzite structure with layer morphology in ZnS.The content of wurtzite structure tends to increase with increasing deposition temperature and H₂S/Zn mole flow ratio, which decreases infrared transmittance of ZnS.The formation of wurtzite structure is related to partial pressure of sulphur in deposition atmosphere.Therefore, ZnS bulk materials should be deposited at lower temperature and H₂S/Zn mole flow ratio to obtain unitary sphalerite structure.