The mixture distribution and combustion characteristics in a DISI optical engine with a single cylinder were investigated under homogeneous and stratified charge modes. The process of mixture formation was observed using tracer Laser Induced Fluorescence (LIF) technique.3-pentanone as tracer was employed. The 266nm harmonic beam of the Nd:YAG laser was used to excite the tracer in the motored engine. A part of piston cavity was made of quartz to visualize the processes of mixture formation. Two different injection timings, which are 270oBTDC and 115oBTDC, were set to simulate both charge modes. The effect of injection timings on the stratified mixture distribution and combustion was investigated. Fuel distrbution surrounding the spark plug was particularly observed from LIF images. From these experimental information under non-combustion and combustion atmosphere, it will be predicted the region where pollutant emissions could be formed.