Ignition delay times for n-butanol/methyl hexanoate blend fuels under an O-2/N-2 atmosphere were measured in a rapid compression machine at compressed pressures of 11, IS, and 20 bar with a compressed temperature between 660 and 830 K. A kinetic model for n-butanol/methyl hexanoate fuel blends was built to predict the ignition delay and simulate the combustion process. The main reaction pathways involved in the oxidation process of fuel blends under low-medium-temperature ranges were recognized. Over the conditions researched in this study, ignition delay of fuel blends showed three-stage oxidation, namely, cool flame, negative temperature coefficient range, and high-temperature oxidation. It is found that the ignition delay times of fuel blends decrease with the increase of the pressure at top dead center and the proportion of n-butanol in blend fuel. Both methyl hexanoate and n-butanol show two-stage heat release in a low compressed temperature range and single-stage heat release in a high-temperature range. n-Butanol has a suppressing effect on the reaction pathways of methyl hexanoate in low-temperature oxidation and a slight effect in high-temperature oxidation.