The volume of fluid method was used to analyze the flow process in pressure swirl injector. SLR camera and phase doppler anemometry were used to measure the spray characteristics of swirl injector and gas-liquid double swirl coaxial injector. Results show that the total pressure loss occurs mainly in inlet section, convergent section, and columned section of swirler trough. The longer the columned section is, the thicker the liquid film and the smaller the spray cone angle is. The range of spay particle distribution increases gradually along the radial direction while the axial velocity distribution decreases firstly and then increases along radial direction. Spray characteristic of gas-liquid double swirl coaxial injector is greatly influenced by gas-liquid ratio (GLR). While GLR is small enough, swirling air increases the spray cone angle and decreases the range of particle distribution; while GLR is large enough, the expansion of air compresses the spray, pushing large droplets to the center of the spray. And at the edge of spray locates small droplets from second atomization.