This paper introduces the newly developed PIV/LIF-PIV diagnostic methods which are capable of simultaneously measuring the flow fields of fuel droplet/vapor and the ambient gas under the nonevaporating/evaporating conditions.Two CCD cameras with high resolution are placed on the opposite side of a constant volume vessel and synchronized to photographing a spray injected from a single-hole nozzle injector.In the non-evaporating condition,the liquid phase flow is visualized through the Mie scattering image of the spray droplets directly while the gas phase flow is traced by the fluorescent(water solution of Rhodamine-B)dying tracer.In the evaporating condition,the vapor phase flow at the tip area of the spray is measured by the silicone particle scattering method while the ambient gas flow is measured by visualizing the heat resistant fluorescent(glycerin & Rhodamine-B)dying tracer.The digital image processing method and the measuring accuracy are discussed in detail by adjusting several parameters.The spray/ambient gas mixing characteristics along the distinguished spray/ambient gas interface were investigated quantitatively according to the simultaneous measurement results.