In the noncatalytic partial oxidation process, autoignition of the heated premixed combustible gases is a major source of reactor damage, unstable operation, and even explosion accidents. The knowledge of the autoignition behavior is of great importance to risk assessment and loss prevention in the partial oxidation reactors. The large experimental effort could be reduced if a reliable modeling procedure is available to identify the safe operating conditions. In this work the reliability of the detailed kinetic modeling method was investigated by comparing the simulated results with the experimental data reported in the literatures. It was found that the USC II mechanism gave the best predictions on the ignition delay times for the methane/air mixtures with equivalence ratios of 3.33 and 6.67. This mechanism was used to extrapolate the ignition delay times in the industrial partial oxidation process. The effects of initial temperature and equivalence ratio on ignition delay times were also investigated. The species concentration profiles were analyzed to understand the underlying ignition chemistry. The sensitivity analysis was carried out for the identification of the main reactions affecting the autoignition process.