Abstract: In this work, the distribution coefficient of RuNO nitrato and nitro comple-xes in HNO_3-TBP-kerosene system is determined on the basis of D. J. Pruett's work.The influence of various factors on the distribution coefficient is studied,including the type of feed solution, extraction time, nitric acid concentration,temperature and concentrations of TBP, DBP and long-chain acidic alkyl phos-phates. It is found that the distribution coefficient of RuNO nitrato complexes incre-ased with the aging time of RuNO Complex feed solution.