Unsulphonated oil，separated from petroleum sulfonate products，was oxidized and saponified，as a result，the petroleum carboxylate was obtained and the productivity of surfactants was increased by more than 25%. The compounds of petroleum sulfonate with petroleum carboxylate could produce ultra-low interfacial tension with Daqing crude at the range of Na₂CO₃ 6—12 g/L and surfactant 1—3 g/L. Considering the fact that the activity of petroleum sulfonate products decreased after unsulphonated oil being separated，the sample containing unsulphonated oil was oxidized and saponified directly and the mixed products of petroleum carboxylate and petroleum sulfonate were obtained，resulting in the productivity of surfactants was increased by more than 8% and the unreacted oil content decreased by 10%. The interface activity remained or slightly improved. The alkaline/surfactant/polymer combined systems using the above oxidation product as surfactant had good long-term stability of interfacial activity and could keep the initial ultra-low interfacial tension of 10^-4 mN/m of orders of magnitude during the store-test period（six months）