Abstract: Diamond films can be used as infrared-transmittance protective coatings on ZnS due to its excellent properties.However,direct deposition of diamond films on ZnS by chemical vapor deposition has been proved to be impossible.The methods of adding interlayer to deposit diamond film and optical brazing technique for bonding diamond films to zinc sulfide for improving the properties of the ZnS window were reviewed in this paper.And the optical application and the difficulties of the CVD diamond were introduced.Finally,the future direction of CVD diamond film development was presented.