The objective of this paper is to investigate the influence of air ejecting on the fuel spray and atomization characteristics of a pressure swirl nozzle in a Stirling engine by using high a speed camera and a FAM laser particle size analyzer. The experimental results indicated that the air ejection produced good effects on the spray morphology. With the help of ejection, the spray drip phenomenon disappeared and the spray diffusion increased greatly. The results also indicated that the air ejection enhanced fuel atomization quality, the droplet sizes tended to be smaller and the size distribution was more uniform.