Abstract: According to the problems existing in the current separation process of rare earth, the systematic optimization study on the separation process of the mixed light rare earth is carried out in the paper.The traditional separation process is substituted by fuzzy separation, and their technical and economical index are compared.The results show that fuzzy separation can get good separation efficiency, and can reduce consumption of acid and alkali by a wide margin, meanwhile, decreases the cost of filling cascades of rare earth and organic phase.Not only the cost of production is reduced, but also the cost of filling cascades is saved.