Homogeneous Charge Induced Ignition (HCII) combustion is believed to be a promising approach to achieve clean and high efficiency combustion. HCII can be realized by using port-injection of the high-volatile fuel (gasoline) to prepare in-cylinder homogeneous charge and direct injection of the high-ignitable fuel (diesel) near the top dead center to control the start of combustion. In the current study, a numerical study was carried out to understand the mixing and auto-ignition process in HCII combustion. A multicomponent chemical kinetic mechanism for gasoline and diesel, consisting of n-heptane, iso-octane, ethanol, toluene, diisobutylene and n-decane, has been developed for predicting their ignition and oxidation. The final mechanism consists of 104 species and 398 reactions. This mechanism was validated with the experimental data of ignition delay times and laminar flame speeds for each component and real transportation fuels. Then the mechanism was coupled into HCII CFD simulation. The simulation exhibited good performance in capturing the combustion processes of HCII. The trends of measured data for each emission were well predicted. It was found that, in HCII, the first stage of heat release was mainly caused by the ignition of diesel. Then the combustion spread across the gasoline charge, leading to the second stage of heat release. The unburned hydrocarbon in the crevice might be one of the main reasons for the high HC emissions of HCII. Overall, the good agreement between predicted and measured data indicated that the current mechanism could be used for duel-fuel combustion mode in practical applications.