In order to reveal the influence of anti-clay swelling agent of quaternary ammonium salt cationic polymer on the stability of heavy oil emulsion，basing on the factor of on-site produced liquid of cycle steam stimulation in NB35-2 oilfield，W/O emulsion was prepared by high-temperature high-pressure autoclave. The effects of anti-clay swelling agent on oil-water interfacial tension and interfacial shearing viscosity，apparent viscosity and emulsion dehydration rate were studied. The results indicated that oil-water interfacial tension decreased and interfacial shearing viscosity increased with increasing anti-clay swelling agent concentration. With the increase of shear rate，oil-water interfacial shearing viscosity increased and finally reached stability when anti-clay swelling agent concentration was constant. The temperature had great effect on the property of emulsion. The anti-clay swelling agent could not form a stable emulsion with crude oil at 55℃. The emulsion was stable and its apparent viscosity increased with increasing anti-clay swelling agent concentration when emulsification temperature was 100℃ and 150℃. Apparent viscosity of emulsion increased and emulsion dehydration rate decreased with increasing emulsifying temperature. When anti-clay swelling concentration was 0.5% —10% ，the emulsion was stable and dehydration rate was 0 at 150℃ . Anti-clay swelling agent of quaternary ammonium salt cationic polymer could reduce oil-water interfacial tension and increase interfacial film strength and the stability of W/O emulsion.