Trioctyl phosphine oxide (TOPO) was used as the model of TRPO and its ,γ, radiolysis was studied. The irradiated samples were dissolved in cyclohexane (CH),then extracted with 5% Na,2,CO,3, and subsequently extracted with distilled water. Emulsification appeared in the process of water extraction. The extent of emulsification depended on the dose absorbed and pH of the system. It increased with the increasing of the dose absorbed, but the total G value decreased. The structures of radiolysis products were identified by IR spectra, UV spectra and element analysis. The results demonstrated that it was the oligomer of TOPO, phosphinic acid and its ester that induced emulsification.