Abstract: This paper has found an elution agent, Mn²⁺-containing sulfuric acid, which has the ability of enhancing the column efficiency of the cationic chromatographic separation of UO₂²⁺ and U(Ⅳ) and of improving the symmetry of their chromatography.In further study, we found out the diffusion process of UO₂²⁺ and U(Ⅳ) in resin can be accelerated with Mn²⁺-containing sulfuric acid agent about 20 and 400 folds respectively.The activation energy of diffusion of UO₂²⁺ and U(Ⅳ) has also beenidetermined in the range of temperature 25-45℃by using the Mn²⁺-containing sulfuric acid as desorption agent. Under the corresponding temperatures, the plate heights h of UO₂²⁺ and U(Ⅳ) are obtained from elution curves respectively, comparing the ratios of Bvalues of different temperatures with the ratios of h' values under corresponding temperatures, we have clearified that the column efficiency under present elution condition is determined by the particle diffusion process and that the effect cf Mn²⁺ ion was attributed to the great enhancement of the particle diffusion process of UO₂²⁺ and U(Ⅳ).For further improving column efficiency, macroreticular ion exchange resin of fine particles Was used. The wriggle pump was used as driving source to overcome the difficulty of corrosion of inorganic acids in a pressured chromatographic separation equipment. After studying the experimental factors, such as stationary phase, operation temperature and elution agent, the optimum coditions for separating UO₂²⁺, U(Ⅳ) and Fe²⁺ or UO₂²⁺ and Fe³⁺ have been established.