Abstract: With the advancement of carbonate reservoir exploration and development in China, the issue of safety drilling in high sulfur carbonate reservoir has attracted more and more attention. Gas cut is one of the most common phenomena in drilling sour natural gas wells, and it is closely related to safety drilling. Beginning from the modes of gas cut during the process of drilling sour natural gas wells, this paper classifies the modes and discusses the principle, the occurrence condition and interrelation of each mode. And then, the research thinking and methods of direct gas cut from qualitative study to quantitative study are proposed, the focus and difficulties in the research in the field are pointed out, so as to provide theoretical basis for forecasting of the amount of gas cut and taking appropriate well-control measures.