Wet Gas Scrubbing (WGS) is one of the important steps in Fluid Catalytic Cracking (FCC) process, which removes SOx from the flue gas. The gas-liquid cyclone separator in the WGS system is adopted to separate the clean gas from alkaline solution. To improve the separation efficiency of the separator, the flow structure therein is to be investigated. In this paper, the pressure and velocity distributions of the gas flow were measured by pressure sensors and five-hole probe. The influence of operating parameters such as the inlet gas velocity and the inlet liquid concentration on the separation efficiency were analyzed. Experimental results showed that the total pressure drop was less than 30 Pa, while the Eu number remained 4.7 x 10(-4) under the inlet gas velocity ranging from 3.7 to 9.8 m/s. The separation efficiency was increased from 82% to 93% with an increasing of inlet liquid concentration from 30 g/m(3) to 60 g/m(3) at a fixed gas velocity of 9.8 m/s. Based on experimental results, a model was formed to predict the pressure drop. Besides, an improved weighting method to calculate the droplet separation efficiency was also given. Furthermore, empirical correlations were proposed to predict the separation efficiency with an average deviation of 1.84%. (C) 2020 Published by Elsevier B.V.