Aiming at elucidating the relationship between injector inner flow, especially injection velocity profiles, and atomization characteristics of liquid sheet, experimental measurement, numerical and theoretical analysis were carried out. Liquid spacial distribution produced by atomization of axisymmetric sheet, which was created by collision of two water jets in opposite direction, was experimentally obtained utilizing paternator. The amplitude of the liquid sheet oscillation was theoretically developed. The numerical results of three dimensional unsteady atomization process through Kelvin-Helmholtz type instability showed qualitative resemblance with corresponding experimental results and theoretical analyses. It was clarified that non-uniform injection velocity profile resulted in velocity distribution with inflection point inside the sheet, thus the sheet became unstable and enhanced atomization. The effect of injection velocity profile on atomization of two dimensional plane jet was also clearly represented.