In order to solve the problem of poor temperature and salt resistance of emulsified viscosity reducers used in chemical flooding and fracturing of heavy oil reserviors，a temperature resistant and salt tolerant emulsified viscosity reducer AFOP was synthesized using bisphenol AF（BPAF），p-hydroxybenzenesulfonic acid（PHSA）and octyl phenol polyoxylene ether（OP-10）as monomers by two steps and three stages method. The structure of AFOP was characterized by IR and GPC. The viscosity reduction effect of AFOP on several kinds of heavy oil at high temperature and high salt was investigated and compared with that of the viscosity reducer used in oil field at the same environment. The optimum synthesis conditions of AFOP was obtained as follows：monomer mass ratio of BPAF to PHSA to OP-10 was 1∶4∶6；under the alkaline condition of the hydroxymethylation stage，the reaction temperature was 80℃ and reaction time was 1.5 h；under the acid condition，reaction temperature was 80℃ and reaction time was 3 h；finally，the polycondensation reaction was carried out at the temperature of 100℃ for 6 h. In the simulated brine system with salinity of 8246 mg/L，the interfacial tension between Bohai crude oil and the AFOP solution with mass fraction of 1.0% after high temperature aging 24 h at 300℃ reduced to 10-1mN/m，and the viscosity reduction rate of heavy oil reached 98% at oil water ratio of 7∶3. AFOP had excellent temperature-resistant and salt-tolerant，and could meet the needs of heavy oil recovery in offshore high temperature and high salt reservoirs.