Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection time and spray angle affects the mixture formations. Thus the purpose of this study was to investigate relationship of combustion and mixture formations according to injection time and spray angle in a common rail direct injection type HCCI engine using a early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection time and spray angle affect the mixture formations and in turn affects combustion in the PCCI engine.