Abstract: In the present study, the sample engine was 168F gasoline engine. By changing the ignition advanced angle and fuel-air ratio, the power, fuel consumption and emission data were collected. By collecting the pressure data and calculating the heat release, effects of the ignition advanced angle and fuel-air ratio on the working process of sample engine were investigated. The optimized ignition advanced angle and fuel-air ratio matching the sample engine were discussed. Through the testing study and theoretical analysis, the sample engine can meet the phase 2 emission standards set by Environmental Protection Agency(EPA) without using the catalystic converter and has the potential to meet the phase 3 emission standards.