Abstract: In Pearl River Mouth Basin, Kaiping sag is located in the deep-water continental slope area beyond the existing continental shelf slope break zone, where oil and gas resources are less explored. It is of great significance to carry out source rock evaluation and clarify its crude oil source for deepening the understandings of oil and gas accumulation in Kaiping sag and guiding the next step of oil and gas exploration. Based on the test data including TOC content, rock pyrolysis, source rock and crude oil biomarker characteristics, the paper systematically analyzes the geochemical characteristics of source rocks of Wenchang Formation and Enping Formation, and conducts the oil-source correlation. The results show that:(1) The argillaceous source rocks of the Lower and Upper Wenchang Formation and Lower Enping Formation tend to be thick in the core area of Kaiping sag and gradually thinned towards the peripheral slope zone, of which the medium to high organic matter abundance and Type Ⅱ₁-Ⅱ₂ kerogen demonstrate that they are in the mature stage as a whole. (2) The source rocks of Wenchang Formation has the low values of Pr/Ph, C₁₉₊₂₀TT/C₂₃TT and low to medium OL/C₃₀H. C₂₇-C₂₈-C₂₉ regular steranes on the gas chromatography-mass spectrum present "V" shape, and C₃₀ 4-methylsteranes have high abundance. The source rocks of Enping Formation have high values of Pr/Ph and C₁₉₊₂₀TT/C₂₃TT, as well as low values of OL/C₃₀H and low C₃₀ 4-methylsterane content, and the distribution of C₂₇-C₂₈-C₂₉ regular steranes shows an inverted "L" shaped pattern. (3) There are two types of crude oil produced from Kaiping sag. As for Type A oil, the Pr/Ph values are within the range of 1.13 and 1.82, the C₁₉₊₂₀TT/C₂₃TT values range from 0.32 to 0.89, the OL/C₃₀H values are between 0.03 and 1.02, and the average relative content of C₂₇ and C₂₉ regular steranes is 26.20% and 46.44%, respectively. The C₃₀ 4-methylsteranes have high abundance. As for Type B oil, the Pr/Ph values are greater than 2.00, the C₁₉₊₂₀TT/C₂₃TT values are between 1.00 and 2.28, the OL/C₃₀H values range from 0.04 to 0.13, and the average relative content of C₂₇ and C₂₉ regular steranes is 9.92% and 65.54%, respectively. The content of C₃₀ 4-methylsteranes is extremely low. (4) Oil-source correlation analysis shows that Type A oil is originated from the hybrid organic matters of Type Ⅱ and Ⅲ formed by plankton and terrestrial plants in lacustrine source rock of Wenchang Formation; Type B oil comes from the deltaic swamp mudstone of Enping Formation in the background of oxidation sedimentation, and the hydrocarbon generation parent material is dominated by Type Ⅲ organic matter formed by terrestrial higher plants. In conclusion, the research has clarified the sources of oil and gas in Kaiping sag, which is of theoretical guiding significance for future oil and gas exploration.