By using the CONVERGE software and the SAGE combustion model, the combustion process of dilute hydrogen ignited by active prechamber jet in a direct injection hydrogen engine was numerically simulated. Based on the experimental data of the hydrogen engine in the literature, the reaction rate of the key elementary reaction in the hydrogen sub-mechanism of the kinetics mechanism version 3.0 for methane oxidation proposed by the American Natural Gas Research Institute（GRI）was modified. Based on the modified hydrogen sub-mechanism of GRI3.0, the indicated mean effective pressure（IMEP）, knocking tendency and emission level of hydrogen engine with active jet ignition and spark ignition were compared under the condition of an equivalence ratio of 0.45. Under the condition that the crank angles at 10% heat release（CA10）are close, compared with spark ignition, four-hole pre-chamber jet ignition achieves a higher peak heat release rate, while the knocking tendency and NO_x emission level increases slightly. The highest IMEPs of pre-chamber jet ignition and spark ignition are close. The flame propagation modes of jet ignition present difference because of the different jet penetration distances caused by different ignition advance angles.