Abstract: To explore the effects of changing intake oxygen volume fraction after installing on-board hydrogen generator, an A151 engine manufactured by BAIC Group was modified. Oxygen injectors were placed in the rear of throttle valves. A self-developed electronic control system was used to control the intake oxygen volume fraction. The experiments were carried out under 1 500 r/min and 42 kPa, 1 500 r/min and 68 kPa, 2 000 r/min and 42 kPa, and 2 000 r/min and 68 kPa operating conditions, respectively. In this paper, the combustion, dynamic, economy and emissions performances of the engine installed on-board hydrogen generator with different intake oxygen volume fractions were studied. Experimental results show that the increase of the intake oxygen volume fraction can enhance combustion, and improve the power of the engine. The torque increases at most 50%. The economy is improved under particular conditions, and the fuel consumption is reduced at most 18.6%. HC emissions decrease at most 63.15%, while the NO_x emissions increase under all conditions.