In other to enhance extraction yield of Tc, the extraction of Tc(TcO4-) in a simulated solution by means of adding a small amount of n-octyl(phenyl)-N,N-diisobutyl carbamoyl methyl phosphine oxide(CMPO) in the 30% tributyl phosphate/ n-dodecane(hereafter described 30% TBP/xM CMPO) was investigated, and effects of nitric acid and CMPO concentration for the selective co-extraction of Tc, Np and U were studied. The extraction of Tc(DTc-TBP/CMPO) with 30% TBP/xM CMPO was occurred by competing reaction between H+ ion concentration in aqueous phase and free TBP and CMPO concentration at less than 0.8M HNO3. Above 1 M HNO3, however, DTc-TBP/CMPO depended on only the free TBP and CMPO concentration. In the presence of U, the extraction of Tc(DTc-U-TBP/CMPO) with 30% TBP/0.02M CMPO occurred by a NO3- ion exchange mechanism through complex formation of TcO4- and U in organic phase. K2Cr2O7 was an effective oxidant of Np at 1 M HNO3. At 1 M HNO3, 0.001 M K2Cr2O7 and 30% TBP/0.02 M CMPO, extraction yields of Tc, Np and U were 66.4%, 85.7%, 94.7%, respectively, and those of Am, Eu, Nd, Mo and Fe were 10.1%, 11.1%, 11.5%, 5.1%, 2%, respectively. It was found that the system of 30% TBP/xM CMPO was enhanced the extraction yield of Np, U as well as Tc, and the selective co-extraction of Tc, Np and U from the radwaste solution was satisfied. For the continuous operation by using a mixer settler type extractor, O/A=1 was more effective condition. When the 30% TBP/xM CMPO system was used, Zr had to be pre-removed to prevent the formation of 3rd phase.