Abstract: In the determination of the degradation products of n--octyl thio--ether by γ-radiation of ~(60)Co, alkanes of 8 carbons are found as the main decompositionproducts. Degradation products of D_2HEPA are first esterified by diazomethaneand then analyzed by GC. It is found that the MEHPA in the degradation pro-ducts increases from 1.02% at a dosage of 5×10~6 rads to 52.04% at a dosage of5×10~8 rads. The detection limit for D_2HEPA, MEHPA and TPPA are 1.8×10~(-8)g、1.4×10~(-9)g and 1.1×10~(10)g respectively.