Abstract: In optical surface film coating,the ion auxiliary deposition(IAD) technique has been widely used.Based on the analysis on the operating condition of IAD,this article compares the two kinds of the ion auxiliary deposition techniques using hot cathode ion source and cold cathode ion source and points out that,with the help of cold ion source,the film deposited on the optical surfaces has the better microstructure.In vacuum deposition,using of the cold cathode ion source can reduce the deposition period.