Americium is similar to light rare earths in solvent extraction by HEHEHP. So the fractional extraction process with three outlets, which is widely used on rare earth industrial scale, can be applied to separate Am from La, Ce, Pr, Nd and Sm. The better process parameters can be calculated by the material and distribution balance equations stage by stage with given organic loading. In order to recover 0.99 mole fraction of Am and remove 0.90 mole fraction of light rare earths from the feed solution, in which the mole ratios of La, Ce, Am, Pr, Nd, Sm are 0.140, 0.199, 0.005, 0.109, 0.487, 0.060, the total number of stages needed is 43, that is the extraction sector 18, first scrubbing sector 2 and second scrubbing sector 23. The fractional extraction process with three outlets is simpler and more convenient than two fractional extraction processes with two outlets.