As a solution for large-scale utilization of hydrogen energy,hydrogen derived fuel has attracted much attention in recent years. Coupling hydrogen derived fuel power generation can greatly reduce carbon emissions of coal-fired units,which is expected to become an important way for coal-fired units to achieve carbon emission reduction in the future. The thermal calculation was performed on a 300 MW coal-fired unit. The influence of coupled hydrogen derived fuel power generation (mass ratios of 0-100%) on various systems and operating parameters of the unit under different working conditions were analyzed under different working conditions in this paper. The results show that the maximum annual emission reduction is about 1.212 million tons of CO2 after large-scale coupling of hydrogen derived fuel. The variation of unit parameters is related to the characteristics of hydrogen-based derived fuel. When the calorific value of hydrogen derived fuel is high,the exhaust temperature decreases by 2.7-9.2 ℃,the boiler thermal efficiency increases by 0.04-0.91 percent point,and the flue gas mass decreases by 20.1-20.8 percent point. When the calorific value of hydrogen derived fuel is low,the exhaust temperature rises by 2.4-26.2 ℃,the boiler thermal efficiency decreases by 0.18-2.04 percent point,and the maximum increase of flue gas mass is 0.4%. Coupling hydrogen derived fuel has little influence on the original air supply system,denitration and desulfurization system. The induced draft fan needs to be expanded and reconstructed. It is necessary to add the independent combustion system and improve the protection level of field equipment and develop the new capture system to reduce emissions of unconventional pollutants such as secondary organic aerosol,formaldehyde and aldehyde.