In this paper, an experimental investigation on spray characteristics of coaxial swirling injector was performed using the laser-scattering system (Malvern) and the self-designed atomization and sprays test facility. It was analyzed and discussed that the effect of gas injecting pressure differential on the spray mass median diameter (MMD) and spray diameter size distribution exponent (n). The study results should provide theoretic guidance in on going gas-liquid coaxial swirling injector design.