A numerical study was conducted for the research of the fiber coalescence separation flow field.The results show that the pressure field of the fiber coalescence separator shows a slowly decreasing distribution from front to back. The pressure decreases with the increase of thickness. The coalescence pressure drop increases linearly with the increase of flow velocity and thickness. With the increase of porosity, the velocity distribution of the fiber coalescence separator is symmetrical. When the fluid flows into the fiber layer, The maximum velocity occurs in the fiber gap. The distribution of velocity in the fiber gap presents a “M” shape.