Abstract: The anion-exchange behaviour of molybdenum(Ⅵ) and tungsten(Ⅵ) on a strong basic anion-exchange resin(Zerolit FF) has been investigated in hydrochloric acid and complexing agent (tartaric, citric and oxalic acid)-hydrochloric acid systems containing various kinds of organic solvent by means of batch method. The main factor effecting of organic solvent on the distribution of molybdenum(Ⅵ) and tungsten (Ⅵ)bet-ween resin and solution phases and the distribution mechanism are discussed. The results indicate that adding organic solvent favors complex-forming and increases the stability of the complexes. The possibility is offered for separation and concentration of trace amounts of tungsten(Ⅵ) from macro amounts of molybdenum(Ⅵ).