The main aim of this reserch was to separate cerium and lanthanum elements from a pregnant leach solution obtained from rare earth bearing in sulfate media by solvent extraction process. Three organophosphate extractants including (2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic mono-2-ethyl oxyl ester (PC88A and tributyl phosphate (TBP) in the kerosene diluent were used for the separation pricess. The effect of various parameters including extractant concentration, organic to aqueous phase ratio, stirring speed, pH, extraction time and saponification stage on the extractions were investigated. Results showed that at 15 % (v/v) of D2EHPA extractant, in kerosene diluent, initial pH of 3, extraction time of 5 minutes, aqueous to organic phase ratio of 1 and stirring speed of 400 rpm, the extraction for cerium and lanthanum was more than 97 %. It was found that for 15 % (v/v) PC88A the extraction of cerium and lanthanum were 59 and 85% before the saponification process, respectively. However, after saponification with 10 % NaOH , the extraction increased to 99 and 96 %, respectively. Also, for 15 % (v/v) D2EHPA the extraction before saponification process about 97 % which was increased to higher than 99% after saponification. The positive effect of saponification process was attributed to the replacement of hydrogen ions from the organic phase sodium ions which leads to decrease pH drops during the process. Also, the maximum separation factor of cerium to lanthanum (? Ce/La ) was 3.3 for the mentioned optimal conditions for both D2EHPA and PC88A extractants, The results of stripping experiments with showed that the back-extraction for cerium and lanthanum were 99.1 % and 82.6 %, respectively