In this work, the effects of fuel temperatures and pressure drops on the flow field and spray characteristics of a pressure-swirl atomizer were discussed using the Particle Imaging Velocimetry (PIV), Planar Laser Induced Fluorescence (PLIF) and Laser Particle Size Analyzer (LPSA) methods. Then the air-blast atomizer was selected to study the interaction of initial atomization and flow field. The effect of fuel-air ratio on the air-blast atomizer were also considered, where the fuel-air ratio was varied by adjusting mass flow rate of the air and fuel respectively. The results show that the spray angle of the pressure-swirl atomizer increases first and changes a little after the pressure drop higher than 0.5 MPa. However, more fuel concentrate on the central region, which is mainly caused by the increase of the proportion of small droplets with lower centrifugal force. The fuel temperature can improve the spray angle only in lower pressure drop, and it has a little effect under higher pressure drops. In addition, the fuel pressure drop has an obvious influence on the fuel distribution and flow field near the nozzle exit compared with the downstream. For the air-blast atomizer, the spray angle increases compared with the pressure-swirl atomizer for the introduction of swirl air. Furthermore, the spray angle decreases with the air mass rate increasing, and it increases with the fuel mass rate increasing. The distribution of velocity and droplet near the nozzle exit is influenced by the air mass rate, and the fuel mass rate mainly affects the distribution in the downstream. The fuel accumulates in the annular area below the nozzle, and the distribution of it changes little with the development along the axial direction.