SThe droplet characteristics of the air-assisted gasoline injector was investigated. A Phase Doppler technique was used to measure droplet diameter and its velocity. The size-classes technique was employed and found to be the best way to understand what kind of droplet is existing in shear flow induced mushroom vortex at spray shell. The detail spray characteristics near nozzle was discussed and the double shell structure was found. The droplets of less than 20 μm can be entrained into mushroom vortex, while the larger of over 30 μm penetrates straight to downstream. The slip velocity and relative Reynolds number were used in data analysis in order to understand the momentum transfer occurrence region due to strong drag force. The spray animation was demonstrated with the ensembled / size-classified droplet, which was found to be the powerful tool to understand spray formation and dispersion process.