Steam flooding is an effective way to develop extra-heavy oil reservoir. However, when the steam flooding process enters into the exhaustion stage, considering lower heat utilization, higher water and poor development performance, how to enhance heavy oil recovery in the post steam flooding process is a large challenge. This paper provides various experiments studying on non-condensable gas-assisted steam flooding. Specifically, the effects of CO2 and N-2 injection on the physical properties of extra-heavy oil were analyzed by High Temperature High Pressure (HTHP) PVT experiments. The effects of CO2 and N-2 on the interfacial tension were studied using Axisymmetric Drop Shape Analysis (ADSA) system and the heat transfer characteristic of core which was saturated with N-2 or water was studied with the sand pack model. Finally, different non-condensable gas (NCG)-assisted steam flooding experiments were conducted using the sand pack model. The results showed that the non-condensable gas dissolving into extra-heavy oil could effectively reduce the oil viscosity and density, and then increase the oil flow capability. The higher pressure and lower temperature was, the smaller the interfacial tension (IFT) was. Compared with N-2, CO2 could significantly reduce the extra-heavy oil viscosity and IFT. But N-2 could increase the sweep efficiency and heat utilization of steam. Compared with steam flooding process, non-condensable gas-assisted steam flooding process could prolong the anhydrous production period and increase the anhydrous recovery. Meanwhile, the non-condensable gas-assisted steam flooding process could increase the oil relative permeability and reduce residual oil saturation. The earlier implementing non-condensable gas-assisted steam flooding, the better the development performance would be.