In order to understand the selfpulsation characteristics of the gas/liquid openend swirl coaxial injector, the atomization test in the atmospheric environment is carried out by adopting the shadow method and the dynamic measurement system. The exit of injector nearby presents a periodic spray process significantly with upstream transient pressure responding repeatedly, while selfpulsation happens. Moreover, the frequency of former pressure, acoustic pressure and spray graphics are highly consistent, ranging from 1 583 Hz to 5 634 Hz. Through analyzing flow rate discipline, its concluded that the injection pressure always presents increasing due to the interaction of gas phase and liquid phase, whether the atomization field displays stable or selfpulsation. As well, liquid flow has stronger influence on the injection pressure than gas flow. The results show that selfpulsation frequency increases with gas phase and liquid phase mass flow, and is relatively sensitive to liquid phase mass flow. As the liquid mass flow growing to critical level, the selfpulsation disappears. Then the selfpulsation frequency keeps improving slowly with gas mass flow increasing. The openend swirl coaxial injector has the upper and lower liquid phase boundary condition generated selfpulsation, and the range widens as gas phase increases. So the gas phase promotes selfpulsation, however liquid phase hampers the development of the selfpulsation. When the liquid swirl injectors wall is thickened, the liquid film thickness increases and the dimensionless gas core shrinks. Furthermore, the selfpulsation frequency of the new coaxial injector is larger than that of the original one.