At present, large and cumbersome gravity sedimentation separators are generally used in the separation of liquid and gas in the wellbore during emergency blowout or circulating degassing in drilling, and innovation and improvement are urgently needed. In this paper, CFX commercial simulation software is used to analyze the cut-in cyclone separator, and the axial inlet type cyclone separator with different length ratios of cylinder-cone section in swirling flow section under different flow channel structures, and carried out indoor simulation and field test verification. The results show that the axial inlet type cyclone separator is more suitable for gas-liquid separation than the cut-in cyclone separator, and the separation can be well improved by increasing the length-diameter ratio of the cyclone section under the cut-in cyclone separator structure. Finally, the experimental separation efficiency reached 99%, and the field test separation efficiency reached more than 98%. This greatly improves the separation efficiency of liquid and gas during the drilling process, and also plays a certain role in promoting the separation of gas and liquid in the entire oil and gas industry.