Abstract: In the separation of rare earth elements with α HIBA-cation exchange chromatography,. two gradient elution techniques, pH-gradient or concentration gradient, are usually used-It is considered that the two gradients are in fact both concentration gradient of a HIBA anion. For routine analysis a simple gradient device is preferred which consists of two-identical cylindrical vessels and operates under pressure of nitrogen. The mixing vessel contains 150 ml of 0.75M α HIBA solution at pH 2.50, and the reservoir vessel, 150 ml of 0.50M α HIBA solution at pH 4.50. A Stainless steel column (φ4×500 mm) was filled with 2×8 cation exchange resin (20-30μm). During the elution at 80±0.5℃, the flow-rate was adjusted to. 0.7 ml/min by regulating the pressure of nitrogen. Ten rare earth elements were completely separated within seven hours without cross contamination. The recovery tor each rare earth element was above 95%.The effect of four solutions for initial loading of the column on the band was examined: (1) The rare earth nitrates dissolved in 0.5M α HIBA solution at pH 3.20. (2) The solution of rare earth nitrates adjusted to pH 3.0-3.5 with ammonium hydroxide. (3) The rare earth hydroxides dissolved in 0.5M α HIBA solution at pH 3.20. (4) The rare earth nitrates dissolved in dilute HNO3 solution at pH 2.5-3.0. The experimental results; indicated that the fourth solution for initial loading of the column is the best. Maximum rare earth concentration occurred on the top of the column, and adsorbed band is narrower. Better results could be obtained from the,first solution, but the rare earth precipitates were sometimes separated out from the solution after dissolving. Based on the above mentioned facts, a procedure was proposed to separate and determine individual rare earth radioactive nuclides from the fission products, and good results were obtained when it was applied for the determination of the fission yields of the rare earth nuclides.