In this study, a new pressurized weighted-sum-of-gray-gases (WSGG) model of a H2O/CO2 gas mixture under pressurized conditions was proposed to calculate the radiation heat transfer of various pressurized combustion equipment. The new WSGG model and its parameters, which are suitable for a pressure range of 1-30 bar, was developed based on the statistical narrowband (SNB) model of EM2C laboratory. Moreover, its temperature range is 500-2500 K, path-length range is 0.001-60 m, and the range of the molar ratio for H2O/CO2 is 0.125-4. Therefore, the new WSGG model is suitable for many fuels under pressurized conditions. The one-dimensional case results demonstrate that the new WSGG model can well predict the radiation heat transfer of the gas mixture under pressurized conditions compared with the benchmark model. In addition, the new model was used to study the effect of pressure on the radiation heat transfer of the gas mixture. The results show that increasing the pressure within a certain range could enhance the radiation heat transfer of the gas mixture, and this effect was also associated with the temperature, the molar ratio and the path-length. In conclusion, the new WSGG model can be applied to the calculation and research of radiation heat transfer in pressurized combustion chambers, such as pressurized boilers, gas turbines, internal combustion engines and aircraft engines. (C) 2018 Elsevier Ltd. All rights reserved.