Abstract: In the middle and later stages of shale gas production, the output declines and the pressure of the gas well decreases. In order to ensure smooth transmission of the product gas, the gas compressor is needed to boost production. Because the shale gas has more particulate impurities than conventional gas, if the impurities are not separation incompletely and go into the downstream, it will cause compressor damage even shut down, which will affect the shale gas production and gathering process, causing huge economic losses. As the last guarantee before shale gas entering the supercharger, the separation efficiency of filter separator is very important. But there are few studies on separation efficiency of horizontal filter separator by numerical calculation method. In this paper, FLUENT software is used for numerical simulation of the horizontal filter separator, and the flow field in the equipment is researched and analyzed. The calculation results show that the filter barrel of horizontal separator can effectively separate solid and liquid particles/impurities. The separation efficiency is high when the liquid particle size is larger than 60 μm and the solid particle size is larger than 30 μm. The overall separation efficiency can reach more than 96%. This method can effectively protect the the compressor lever, optimize the shale gas gathering and transportation technology, and ensure the safe operation of shale gas field.