Abstract: An experiment on the test bench is first carried out to investigate the performance of a hydrogen-enriched engine at low speed,low load and lean conditions in this paper.The hydrogen volume fraction in the intake is kept at 0,1%,3% and 6% for a specified excess air ratio,respectively.A simulation model is built based on AVL Boost software.The measured data,such as cylinder pressure,intake air flow rate and effective pressure,are used to validate and calibrate the model.Then,the performance of a hydrogen-enriched gasoline engine at a specified intake manifolds absolute pressure with different hydrogen volume fractions in the intake and excess air ratios is investigated through the model.Simulation results show that hydrogen enrichment is effective in improving the engine performance at low load,low speed and lean conditions.The engine indicates that the thermal efficiency and working ability are improved with increasing hydrogen addition fraction at lean condition.For a specified hydrogen blending level,the peak cylinder pressure is reduced and the relevant crank angle for the peak cylinder pressure is retarded with the increase of the excess air ratio.Under lean condition,both flame development and propagation periods are shortened,cylinder pressure is enhanced,and the relevant crank angle for the peak cylinder pressure is advanced after hydrogen addition.