Abstract: A simplified model of structural design for round pipe gas-liquid cyclone separators is built and the separator's structural parameter design and calculation are completed through the research on trajectory of drops and bubbles and combined with design experiences of traditional separators. Fluent software is used to conduct numerical simulation and research into velocity distribution and pressure distribution in single-inlet and dual-inlet separators. Axial velocity is upward in the center zone of separator and downward outside the zone, fitted with the empirical correlation of maximum axial velocity and inlet mixture velocity; tangential velocity is zero in the central position of the separator, first increases and then decreases in the radial direction, and it is zero on the wall, while the vortex is divided into two layers on both sides of the maximum value, approximate forced vortex for the inside and approximate free vortex for the outside; radial velocity is less than the tangential velocity and axial velocity in the quantity degree, while it is positive and negative on both sides of the axis, zero in the center position of the separator, first increases and then decreases along the radial direction and zero on the wall. On the section of the lower liquid phase space, the maximum pressure is on the round pipe wall and the minimum pressure in the center. In the axial direction, the pressure gradually increases with the rise of liquid level. Through comparison between simulated results of single-inlet and dual-inlet separators, it is indicated that the dual-inlet separator is subject to the better tangential velocity, radial velocity and pressure distribution symmetry, more stable flow field and less kinetic energy loss, thus confirming that asymmetry of separator flow field is caused by inlet effects under the condition of single-inlet.