Abstract: Mixing hydrogen in natural gas is an effective way for the long-distance and large-scale transportation of hydrogen, but the heat transfer property of hydrogen is diferent from natural gas, and it is still unclear about the adaptability of heat transfer performance of in-service air cooler to hydrogen-mixed natural gas. In order to evaluate the heat transfer performance of air cooler after the mixing of hydrogen in natural gas, a simulation model of horizontal blast air cooler in service was established. Then, the specific heat capacity and thermal conductivity of natural gas at 7?10 MPa, 60?80 ℃ and 0?25% hydrogen mixing ratio were calculated based on the BWRS equation. Meanwhile, the CFD technology was used to analyze the gas temperature difference before and after the air cooler under different working conditions. The results show that: (1) Mixing hydrogen will increase the specific heat capacity and thermal conductivity of natural gas. (2) Reducing the pipeline pressure and the daily treatment capacity of air cooler under standard conditions, increasing the initial temperature of natural gas and mixing hydrogen will increase the temperature diference before and after the air cooler. (3) The existing air cooler could meet the cooling demand of natural gas without structural transformation in the case of mixing hydrogen is lower than 25%.(4) The transportation pressure of pipeline could be increased to stabilize the outlet temperature of the air cooler and improve the pipeline transportation capacity for transportation with hydrogen mixed.