Abstract: The synergistic extraction of uranyl nitrate in nitric acid medium with binary system of DMHMP(di-methyl hexyl methyl phosphonate) and HTTA(2-thenoyl trifluoroacetone) is studied. It is found that synergistic effect occurs during the extraction of uranyl nitrate whth benzene solution of DMHMP-HTTA. The formation of a binary extracted complex UO2(TTA)2·DMHMP is confirmed by the usual slope method and Job's variation. The binary synergistic equilibrium constant is determined to be logβ12= 3.74. A possible structure of the complex of syaergistic extraction is proposed.