For rotary disk atomizer in this paper, the particle characteristics has been investigated with Rosin/Paraffin mixture as the working fluid. The effects of different technological parameters on the ligament number, diameter of ligament, capillary wavelength and particle diameter were analyzed, and the dimensionless prediction model was obtained. The result showed that the ligament number is mainly determined by the Web and the St number, and it is only controlled by the surface tension for low viscous fluids. Due to ligament stretching caused by centrifugal effect, the pinch-off capillary wavelength is about 3.56 times of the ligament diameters, however the actual dominant mode is the short-wave mode. For the fully-ligament mode, the ligament number will remain unchanged with the increasing of pouring flow, while the diameter and length will grow. The diameter of particles is mainly determined by the ligament number and capillary wavelength. The higher the rotational speed is, the larger the tangential slip ratio is, the diameter of particles will not obviously reduce consequently. It is suggested to control the diameter of particles by a disk with a large diameter or improvement of the topological structure of the disk rather than by the method of always increasing the rotational speed.