The pre-chamber sparkplug mode can increase the combustion velocity because it can induce the turbulent jet into the cylinder. Higher combustion velocity can increase the brake thermal efficiency and decrease the knock tendency for hydrogen engines. To explore the effect of pre-chamber sparkplug mode on the combustion characteristics of the hydrogen-air mixture, different equivalence ratios, initial pressures and temperatures were selected to study in a constant volume combustion chamber working with pre-chamber sparkplug mode and normal sparkplug mode. The results showed that the pre-chamber sparkplug mode can accelerate the combustion velocity, increase maximum combustion pressure and decrease the combustion duration at all initial conditions. The maximum combustion pressure of pre-chamber sparkplug mode occurred at the equivalence ratio of 1.0 while it occurred at the equivalence ratio of 1.2 with normal sparkplug mode, which means pre-chamber sparkplug mode can increase the higher brake thermal efficiency and power. The combustion intensity of pre-chamber sparkplug mode was bigger than 1 and the biggest value occurred at the equivalence ratio of 0.6. Moreover, the combustion intensity of pre-chamber sparkplug mode was higher with lean equivalence ratios than that of rich equivalence ratios. Increasing the initial pressure can increase maximum combustion pressure and combustion velocity obviously for pre-chamber sparkplug mode, which was different from the normal sparkplug mode. The initial temperatures had little impact on the combustion intensity. These results showed the pre-chamber sparkplug mode was more suitable to be used in the boosting hydrogen engines to improve the performance. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.