Abstract: The icing cloud inside the icing wind tunnel test section is generated by the Spray Bar System (SBS)which is located at the wind tunnel settling chamber.The icing conditions such as the icing cloud liquid water content (LWC)and the water droplet size (MVD)are deter-mined by the spray nozzle performance of SBS.In this paper,the droplet size distribution and the water flux of the small droplet spray nozzle used in the icing wind tunnel are measured on a spray testing platform by Phase Doppler Interferometer(PDI)and low flow rate flow-meter.The for-ward scattering method was used to optimize the quality of the PDI signal and the reliability of the result.The influence of the water pressure,the air pressure,their difference and the throttle pipe diameter on the atomization characteristics of the spray nozzle are investigated.The results show that:when the pressure difference between water and air increases,the MVD and water flow-mass also increases;as the diameter of throttle pipe of water is reduced from 0.4mm to 0.35mm,the range of pressure difference between water and air increases,and the coverage of the water practical size and flow mass can exactly meet the icing wind tunnel operation require-ments.The water flow-mass ratio of the spray nozzle can reach 11.5 and the droplet diameter range can vary from 7μm to 70μm,which are better than the other similar icing wind tunnel spray nozzles in the world.