Abstract: The traditional cyclone can only get the overflow and the underflow in a single grading.A multi-product cyclone with double overflow pipe structure is presented in the paper.A flow field model of double overflow cyclone is established.By using the theory of multi-phase flow in fluid mechanics, the flow field inside the hydrocyclone is simulated, and the distribution characteristics of the flow field inside and outside the cyclone are obtained accurately, and the formation, development and evolution process of the flow field and the air column are obtained.The influence of structures on the performance of the air column in the double overflow hydrocyclone is numerically calculated.The diameter of the air column in the cyclone increases with the increase of the diameter of the bottom orifice and overflow orifice.When the diameter of the inner overflow pipe is small and the diameter of the bottom orifice, the air column is more chaotic.The results of this study lay a theoretical foundation for analyzing the air column’s influence on vortex motion and optimization of configuration parameters of the hydrocyclone.