Abstract: In order to measure the velocity distribution of dual-media nozzle droplet particles, an on-line measurement system was established based on continuous laser at 532nm wavelength and industrial cameras. The droplet trajectory images were obtained. The Steger method was used to process the particle trajectory images. The velocity distribution of droplet particles was extracted. The results show that the test method for measuring the speed distribution of the droplet particles based on particle trajectory images, meets the requirements of the online measurement.