This study was performed by the numerical approach to investigate chemical behaviors of homogeneous syngas (CO/H₂) with nitric monoxide (NO) in pressurized oxy-fuel conditions. Hydrogen had a dominant effect to the ignition delay time of syngas due to the fast chemistry of its oxidation. Combustion was promoted by NO at the low temperature region. It was by the additional heat release through NO oxidation and production and consumption of major radicals related to the ignition. Two stage ignition behavior was shown in the pressurized condition by the accumulation of H₂O₂ produced from HO₂ radical. Additional NO oxidation was induced by the pressurized oxy-fuel condition to produce NO₂.