Abstract: The SM-series separator researched by Shell Oil Company is a kind of effective equipment for natural gas dehydration and dehydrocarbon process. This paper systematically summarized development, structure and working principle of the SM-series separator. The results indicated that the SM-series separators combining gravitational separation with high-efficiency component parts have the advantages of high separation efficiency and modular components. Therefore, it is suitable for natural gas dehydration and dehydrocarbon unit. Moreover, aiming at the development of SM-series separator, the theoretical research of gas-liquid separation can contribute to obtain the working situations of some component parts and discovery the distribution of average droplet size in gas-liquid separators, which can provide references for optimization design of component parts and performance improvements of the separator.