The extraction performance of uranium(VI) from nitric acid with N-octanoylpiperidine (OPPD) in series of diluents has been investigated. The dependence of extraction distribution on the concentrations of aqueous nitric acid and OPPD and also the temperature has been studied. The experimental results showed that the decreasing order of extraction ability of OPPD is as follows: benzene, dimethyl benzene (DMB), toluene, 1,2-dichloroethene, n-octane, carbon tetrachloride, cyclohexane, chloroform. It cannot be interpreted only on the basis of polarity of the diluents. The interaction between extractant or extracted species and diluent is discussed.