The homogeneous charge compression ignition (HCCI) characteristics of diisobutylene are studied numerically. Numerical results are in accord with the corresponding experimental data. The influence of some key parameters such as initial pressure, equivalence ratio and constituent on autoignition characteristics is discussed and combustion characteristics of diisobutylene in HCCI engine are analyzed. The results indicate that the ignition delay decreases with the increase of pressure and equivalence ratio. The maximum temperature increases with the rise of equivalence ratio, but it does not change with the variation of initial pressure. The 1 pentene isomer ignites significantly faster than the 2 pentene isomer and the ignition delay for the blend directly depends on the proportions of each isomer. It can be found that diisobutylene shows the single stage autoignition. The maximum heat production rate of the 2 pentene is lower than that of 1 pentene, but the 2 pentene still provides good power performance.