Abstract: This study aims to ascertain the accumulation characteristics of natural gas in the deep-water oil and gas fields in the Qiongdongnan Basin. To this end, it performed continuous multi-component carbon isotope measurements for natural gas wells in the basin. Based on the comparative analysis of a continuous carbon isotope profile from a key well in the basin and the carbon isotope values from key intervals in surrounding wells, this study delved into the genetic types and sources of natural gas in the key well. The results show that dry gas occurs above the first member of the Sanya Formation, dominated by biogenic and secondary biogenic gases. In contrast, wet thermogenic gas exists below the second member of the formation, primarily including associated gas. Besides, natural gas in the BD21-1 block originates from two sources: Eocene high-maturity oil-formed gas and low-maturity gas with a special genesis from the Yacheng Formation. Overall, multi-component carbon isotope logging is effective in investigating the genetic types, sources, and maturity of natural gas.