Cerium is the most abundant element of the rare earth group. The more important minerals containing cerium are allanite (also known as orthite), bastnaesite, cerite and monazite. Cerium is characterized chemically by having two stable valence states, Ce4+, eerie, and CeH, cerous and this property underlies several technological uses. The ceric ion is a powerful oxidizing agent but when associated with strongly coordinating ligands. Especially, oxygen-donors is completely stabilized and indeed cerium oxide CeO2 (ceria) is the form of cerium most widely used. The recognition that cerium was a unique element and its relationship to other elements, were factors in the gradual development of thePeriodic Table concept. The separation and identification of all the individual 4f elements, cerium included, caused considerable confusion one hundred years ago but the understanding of atomic structure. In this paper, the authors are study using liquid-liquid extraction by the organic phase containing the mixture of triphenylphosphine oxide and 2-ethylhexyl 2-ethylhexyl phosphonic acid in nitric acid solutions have been researched for separation rare earths and cerium from Yen Phu group light ore rare earth. Rare earths in the organic phase can be scrubbed by nitric acid from 1M to 4M. Thorium by HNO3 6 M and Cerium after reduced to Ce(III) is scrubbed by nitric acid 4 M and H2O2 (10 percent).