Abstract: The effect of γ-radiation on extraction and stripping or retention of technetium by 30 % trialkyllphosphine oxide (TRPO) in kerosene is investigated. Results show that the distribution ratio of Tc does not change remarkably when absorbed dose varies from 1×10 6 Gy to 5×10 6 Gy and pre-equilibrated acidity ranges from 0.5 mol/L to 4 mol/L, and the stripping performance of Tc changes noticeably when 5.5 mol/L HNO 3 and 5 % Na 2CO 3-H 2O are used as stripping agent, respectively. In order to ascertain the reason of retention, some acidic degradation products of TRPO, including phosphinic and phosphonic acids, are synthesized. By lavation with 5 % Na 2CO 3, deioniozed water and vacuum distillation, irradiated 30 % TRPO-kerosene-1 mol/L HNO 3 system is separated into alkali-extracting substance, aqua-extracting substance and high boiling point substance. The influences of these degradation products are studied by adding them into the original extraction system respectively. The results indicate that the component of high boiling point is the main factor causing retention, while others have no apparent influence.