In view of the technical problems faced by high-temperature thermal recovery technology for offshore heavy oil，such as high cost，high risk，and the limited oil-increasing effect of single hot-water flooding，a synergistic hot-water flooding technology based on self-developed temperature-resistant multifunctional polymers TMP was systematically evaluated to clarify its mechanism of enhancing oil recovery and its potential for field application. A research approach integrating laboratory experiments and numerical simulations was employed and the performance of polymer TMP in viscosity enhancement of water，viscosity reduction of oil，interfacial tension reduction，and the disassembly of asphaltene aggregates was systematically evaluated. Using the CMG numerical simulation software，an injection-production well pattern model was established，the displacement process was inversed， and the impacts of static and dynamic reservoir factors on the oil-increasing effect were investigated. The experimental results indicated that at 80 ℃ and a concentration of 1500 mg/L，the solution viscosity of the polymer was approximately 80 mPa s，and it exhibited excellent temperature resistance. It could reduce the oil-water interfacial tension to the order of 10^-1 mN/m. By disassembling asphaltene aggregates，the viscosity reduction rate of crude oil could reach 85% at 80 ℃. The numerical simulation results showed that the enhanced oil recovery rate of polymer-enhanced hot-water flooding could reach 6.0 percentage point，which was significantly higher than that of single hot-water flooding（1 percentage point—2 percentage point）. As for the oil-increasing effect，the polymer played a dominant role with a contribution rate of 80%—90%，while thermal energy played an auxiliary and synergistic role with a contribution rate of 10%—20%. The study determined that the optimal reservoir conditions suitable for this technology were as follows：average permeability＞2000×10^-3 μm²，in-situ crude oil viscosity of 200—600 mPa s，and water-body multiple＜4. The temperature-resistant multifunctional polymer-enhanced hot-water flooding technology， achieved the complementary advantages of "relying mainly on thermal energy to reduce viscosity near the well and chemical energy to reduce viscosity in deep formations" through the synergy of thermal energy and chemical energy，and had the dual effects of expanding the swept volume and improving the oil-washing efficiency. The project design for the Bohai D oilfield demonstrated that this technology could increase the oil recovery rate by 5.9 percentage point compared to water flooding，providing a promising new approach for the economic and efficient development of offshore heavy oil.