Abstract: Distribution ratio and separation coefficient of aluminium，rare earth in naphthenic and chloronaphthenic acid systems with different extractant saponification value have been studied respectively in different acidity and aluminium concentration.The results show that optimized process parameters are all M_Al=12.5 mmol/L，pH=0.10 and 0.35 extractant saponidication value in the two extractant systems.Moreover，separation coefficient of aluminium，rare earth in chloronaphthenic acid is about 4.5 times than naphthenic acid systems.Besides these，avoiding emulsion problem is also advantage of chloronaphthenic acid.So chloronaphthenic acid system has more superiorty.

Key words: Chloronaphthenic acid, Rare earth, Aluminum, Distribution ratio, Separation coefficient