Abstract: Vertical continuous high-resolution logging information is used in logging assessment of hydrocarbon source rock to evaluate the content of organic carbon in mudstone of the formation. This will solve the bottleneck of identifying space distribution of regional hydrocarbon source rock owing to inadequate geochemical data and provide the basis for calculation of reserves and making decisions on oil and gas exploration. The study adopts Δ logR method and is combined with geological statistical analysis and logging information corrected under different geological conditions to assess hydrocarbon source rock. This method used to appraise 191 wells in Langgu Depression. Based on regional and stratigraphic sediment data, it make detailed description of space distribution of high-quality, medium-quality and poor hydrocarbon rock in different stratum series. In Langgu Depression, hydrocarbon source rock developed mainly in Es3 and Es4 with the thickness mainly reaching 700 meters to 3000 meters at the medium and low quality. High-quality hydrocarbon source rock is distributed in small area with short thickness, only 30 meters to 70 meters. High-quality source rock developed mainly in the lake invasion system. With the center of source rock changing, high-quality source rock of Es4 is mainly distributed in the Caojiawu-Yongqing zone while high-quality source rock of Es3 is distributed in Jiuzhou-Gu?an zone.