Separation of liquid droplets from gas-liquid streams is of great importance in various industries, including oil and gas, paper and textile industries. There are different types of gas-liquid separation systems in the industries. Axial flow cyclones are used as one of the widespread separation techniques to separate particles or droplets from a gas stream, which due to high efficiency at high pressure, high gas-liquid flow capacity, lack of sedimentation, etc, are considered advanced equipment as output and Input in horizontal and vertical separator or as independent separators for smaller and more compact design. In the axial flow cyclone that is considered in this study, the gas-liquid two-phase mixture flow enters the cyclone axially through the upper inlet of the cyclone, is rotated by passing through the guide vanes, which, under the resulting centrifugal force, the droplets are thrown to the wall and enter the liquid reservoir through the annular gap and therefore are separated from gas flow. In this project, the axial flow cyclone is numerically simulated using the Eulerian-Lagrangian approach and the two-phase flow model of DPM, the RSM turbulence model and considering the two-way interaction between liquid and gas. The simulation is done in Fluent software. In the first stage of the research, the effect of various parameters and factors on the performance of gas-liquid separation in the axial flow cyclone has been investigated. The observations are as follows: Separation significantly depends on the gas flow velocity and volume fraction of the injected liquid, so that by increasing these parameters, the separation process improves. It has also been observed that increasing the length of the cyclone tube in the central body slightly reduces the separation efficiency, but increasing the density difference between the gas and the injected liquid has a significant effect on increasing the cyclone separation efficiency. In this study, by examining the surface roughness height, wall roughness in the central body of the cyclone has been introduced as an effective parameter in reducing the performance and separation of liquid in the cyclone. In the second stage of the research, two innovative approaches have been proposed to improve the separation performance of liquid droplets with a small diameter (5 micrometers). In the first approach, the use of porous material and cellulose paper as a moisture absorber along the cyclone outlet area is proposed. The results show an increase in separation efficiency due to the use of a porous material that acts as a liquid-gas filter. This study has been done in different thicknesses of porous material and even by increasing the diameter of the cyclone along the outlet area as a step. In the following, the parameters affecting the performance of the porous material are investigated. The results show that reducing the permeability and porosity percentage reduce the flow velocity in the porous material as well as the boundary between the porous material and the main stream in the cyclone, which may reduce the possibility of re-entrapment of liquid droplets trapped on the porous material networks and cyclone wall by the Gas stream. The second approach to improve the separation efficiency of the liquid remaining in the gas stream is to use the axial flow cyclone in two stages. This approach is a new method of separation in cyclones for small droplets even 5 micrometers in diameter. The results of two-stage cyclone show a 37.5% increase in separation efficiency due to the use of the second stage of separation in the cyclone. In this method, the pressure drop due to the flow re-rotation has increased to 31.32 kPa, which can be ignored in contrast to the operating pressure of 8.5 MPa in the cyclone and its optimal efficiency. Keywords: Gas-Liquid, Cyclone, Separation, Numerical simulation, Porous media, Two-stage.