Abstract: Hydrogen and ammonia have been widely concerned as clean energy sources, and the mixed combustion of the two can promote the application of hydrogen and ammonia in practical combustion. In this paper, a relevant reaction model is established with the help of Chemkin simulation platform, and the combustion process is simulated by Otomo mechanism with hydrogen-ammonia gas mixture as fuel and air as accelerant. The ignition delay time, laminar flow combustion speed, adiabatic combustion temperature, NO emission and other combustion characteristics of the mixed gas were simulated varying the equivalent ratio, initial pressure and hydrogen ratio in the fuel. Chemical kinetic analysis was carried out on the laminar flow flame structure, ROP yield of H and OH radicals and sensitivity of NO generation under different working conditions. The influencing factors and essential reasons of the combustion characteristics of hydrogenammonia mixed combustion were deeply investigated. The results show that pure ammonia gas has long ignition delay time, slow laminar flow combustion rate, improved combustion characteristics after hydrogen mixing, and increased the adiabatic combustion temperature of the flame, but the higher the proportion of hydrogen mixing, the more NO emission.Considering a series of combustion characteristics of hydrogen-ammonia mixed combustion and the costs and benefits of hydrogen mixing and pressurization, this paper recommends 15% hydrogen, equivalent ratio φ=1.1, and pressure P=0.2 MPa as the optimal conditions for hydrogen-ammonia mixed combustion.