Abstract: Baiyun sag in the Pearl River Mouth Basin is rich in oil and gas resources and has great exploration potential. The development of strong overpressure in the deep target layer is studied in this article, focusing on the causes and compaction effects of overpressure in the deep Baiyun depression; Using 3D seismic data and geophysical logging data to gain a detailed understanding of the deep overpressure in Baiyun depression, using comprehensive compaction curve method and basin simulation technology to process drilling and logging data, and analyzing the causes of abnormal pressure in the deep layers. Summarize the pressure distribution pattern and the causes of abnormal high pressure based on the principles of zoning and layering, and use fluid potential evaluation methods to predict the migration and accumulation of deep oil and gas in Baiyun Depression, providing a basis for the next exploration deployment in Baiyun Depression. Research suggests that the areas where overpressure develops in the Baiyun Depression mainly include the center of the main depression, the east of the main depression, the southwest of the main depression, and the north slope (sorted by the scale of overpressure development); Deep overpressure develops in the Zhuhai Formation and below; The contribution of overpressure causes in different layers is also different; Among them, the main causes of overpressure in the Enping Formation are compaction pressurization and hydrocarbon generation pressurization, while the main sources of abnormal pressure in the Zhuhai Formation are compaction pressurization and transfer type overpressure. The undercompaction effect varies among different blocks. In addition, influenced by factors such as geothermal energy, the chemical compaction processes developed in each block are different. Due to the strong development of overpressure in the main depression. Therefore, the momentum is relatively high, and small depressions such as Dongwa and Xiwa also formed high-value areas of momentum in the late stage; The main depression to the north slope, the main depression to the southwest, and the main depression to the east have formed obvious low value areas due to their high terrain. The areas with larger gas gradients in the Enping Formation gradually expand towards the slope zone and low uplift, which is conducive to the migration of oil and gas towards the northern slope and the eastern part of the main depression in the later stage.