Ignition enhancement effects of N2 and O2 plasma jets (PJs) to H2 fuel were numerically investigated. Calculation was conducted for a rectangular test section with inflow Mach number of 1.9. Fuel and PJ which located downstream of fuel injector were injected perpendicularly at sonic speed into main flow. Numerical results were compared with experiments using only N2 PJ and basically agreed to them. With N2 PJ for H2 fuel, N radicals slightly promoted combustion reactions, but, NO and NO2 did not show ignition enhancement effects in this calculation condition due to the low pressure of main flow. Meanwhile, with O2 PJ, not only O radicals but also high temperature O2 molecules accelerated combustion reactions. Therefore, O2 PJ had much stronger ignition enhancement effects compared with N2 PJ.