Horizontal well multi-component thermal fluid stimulation high efficiency recovery technology is an EOR technology for heavy oil reservoir, which utilizes horizontal well, CO2, N2 and steam. The EOR mechanism is studied through horizontal well multicomponent thermal fluid stimulation experiment and numerical simulation based on the heavy oil reservoir characterization. Compared with the conventional steam stimulation, the horizontal well multi-component thermal fluid stimulation high efficiency recovery technology has three advantages: horizontal well can improve the injectivity and productivity and has a longer-term validity, the CO2 can significantly decrease heavy oil viscosity and residual oil saturation, in addition, the CO2 can also improve the displacement efficiency; the N2 can enlarge the sweeping volume and decrease the heat loss. The field application confirmed that this technology can significantly improve the steam utilization, decrease the injection pressure, improve oil well productivity, extend period of validity, and greatly improve the heavy oil reservoir of offshore reservoir.