Abstract: Homogeneous Charge Compression Ignition (HCCI) engine has become a potential power unit to satisfy the stricter emission regulations and obtain higher thermal efficiency values. However, main issues are the uncontrollable combustion of HCCI, which is unfavorable for engine application. Dual fuel application in HCCI is applied to overcome the difficulty in combustion control. There are some research has been done, but the research that focused on the combustion behavior of the dual fuel has not yet been investigated. Current research objective is to simulate and analyze the affecting parameters and the behavior of the dual-fuel HCCI combustion. The simulation was done on constant volume chamber using the SHELL autoignition model. It is shown that initial temperature has the major effect to the combustion delay of dual fuel. Higher initial temperature will shorten the combustion delay. Furthermore, the existence of fuel with higher octane number suppressing the reaction and delay the combustion.