This paper deals with experimental analysis of gas fuel injection by schlieren method. In case of fuel direct injection is applied to a two-stroke engine, the time from injection to ignition is extremely shorter than in a four-stroke engine, and the time is about 1/6 in comparison with four-stroke engine. Therefore, grasping the diffusion and whereabouts of injected gas fuel is important for the to form very suitable mixture around ignition plug. In this study, the purpose is analysis by schlieren method using methane gas as supposing the natural gas fuel direct injection. As a result, we could observe effective diffusion to make homogeneous mixture or stratified combustion.