Abstract: The p-tert-butylcalix［4］arene phosphinoxide derivatives and p-tert-butylcalix［6］-arene phosphinoxide derivatives were synthesized by substitution reaction. IR, ¹H NMR and ¹³C NMR were used to characterize the compounds. The influences of pH, concentration of extractant, extraction time and temperature on the calixarene and its phosphinoxide derivatives’ extraction of U(Ⅵ) were investigated. The results show that the extraction effect of U(Ⅵ) by p-tert-butylcalix［6］arene is higher than p-tert-butylcalix［4］arene, meanwhile, the extraction efficiencies of U(Ⅵ) by the calixarene phosphinoxide derivatives are higher than the extraction efficiencies of U(Ⅵ) by calixarenes. Compared with calixarenes, the calixarene phosphinoxide derivatives’ extraction efficiencies of U(Ⅵ) are increased by 36-49% and 37-61% respectively under the same condition.