A total of 444 mudstone samples were colected from 6 boreholes located in the northemn margin of the south China Sea. These samples represent a sedimentary succession ranging from the Eocene to the Oligocene, which was conducted for palynological analysis. To assure the acquisition of trustworthy paleoenvironmental data, we performed thorough selection on the debris samples, focusing on primary mudtone debris larger than 10mm. Prior to sample processing, an akali treatment (using NaOH) was applied to all samples, followed by sieving to eliminate coarse sediment particles. Subsequently, the hydrochloric acid (36% HCI), hydrofluoritc acid (20% HF) and acetolysis were utilized to extract organic material. Resulting residues, having passed through a 10μm sieve, were meticulously spread onto slides with 50% glycerine, enabling species identification and count of pollen and spores under an optical microscope.