The combustion process in internal combustion engine is dominated by turbulent mixing the injected fuel with the ambient air. Therefore, in order to realize the high efficiency and clean combustion, it is necessary to understand in detail phenomena concerning these turbulent mixing process. Then, as a fundamental work elucidating the mechanism of mixture formation in the turbulent flow field, the gas velocity inside the transient gas jet was measured by PIV method, the concentration distribution of the entrained air was measured by LIF method. In addition, with two fluorescence tracer method proposed in this study, it is possible to measure simultaneous characteristics of fuel and surrounding air flow and concentration distribution. As the result, there is the stronger inverse proportional relation between the change in the ambient concentration and that in the axial turbulence intensity against that in the radial turbulence intensity. The change in the radial turbulence intensity is larger than that in the axial turbulence intensity, as a consequence that in the concentration is larger.