Ignition delay times of di-n-butyl ether (DBE)/oxygen mixtures diluted with argon were measured behind reflected shock waves for the pressures between 1.2 and 4 bar, the temperatures between 1100 and 1570 K, and the equivalence ratios of 0.5, 1.0, and 1.5. A recently developed DBE model was employed to simulate the autoignition process of the homogeneous mixture. Comparisons between the measured and calculated ignition delay times indicate that the model yields fairly good agreement under all test conditions. Results show that the ignition delay time increases with the decrease of the pressure and the increase of the dilution ratio. The ignition delay time demonstrates a strong negative dependence upon the equivalence ratio at high temperatures, and the difference among the ignition delay times tends to decrease when the temperature is decreased. Sensitivity analysis reveals the importance of H-abstraction reactions and decomposition of a fuel radicals in the ignition process of DBE. Reaction pathway analysis confirms that the consumption of DBE is dominated by the H-abstraction reactions at lower temperatures, and when the temperature is increased, the unimolecular decomposition reactions become more important. Comparisons of ignition delay times as well as fuel consumption and radical growth history of DBE to dimethyl ether (DME) and diethyl ether (DEE) for given equivalence ratios indicate that DBE has the strongest overall reactivity, although the reactant concentration of DBE is the lowest.