Abstract: The density functional theory(DFT) was applied to investigate the geometric and electronic properties of a series of xanthate collectors. The reactivity of xanthate collectors was analyzed by using the highest occupied molecular orbital(HOMO) energy,natural population analysis charge,electronegativity and hardness index. It is found that xanthate anions are the active ingredient in flotation solutions,and the bonding atom of a xanthate anion is the S atom in the C-S bond. The HOMO energy can be used to interpret that the flotation activity of straight chain xanthates(C₁-C₆) increases with the alkyl chain growth. The more the branched chains of carbon atoms attached to polar groups in xanthate isomers,the stronger the flotation activity is. The order of the flotation activity of C₃-C₅ xanthate isomers is as follows:tert-alkyl xanthate sec-alkyl xanthate iso-alkyl xanthate.