Abstract: In this paper the 60Co γ-radiplytic products of the solutions of HDEHP-nC12 (n-dodecane) and 0.2M TBP-nC12 and 0.3M HDEHP-0.2M TBP-nC12 are analyzed and determined by gas chromatpgraphy.The H2MEHP arid H3PO4 are produced from radiolysis of HDEHP, and the amount of degradation products is approximately 5-7% of the corresponding extractant with an absorbed dose of 1×108 rads. The stability towards γ-radiation of HDEHP is higher than TBP. The amount of H2MEHP for pure HDEHP system is proportional to the absorbed dose, but the amount of H3PO4 is proportional to the square of the absorbed dose.If the kinetics is treated as consecutive first order reactions, the calculated amounts of H2MEHP and H3PO4 formed agree quite well with the experimental values in pure HDEHP system. Therefore it is suggested that the radiolysis of HDEHP takes place according to the mechanism HDEHP→H2MEHP→H3PO4.