Pore Pressure abrupt change (PPAC), encompassing pore pressure surge (PPS) and pore pressure reversal (PPR), are prevalent phenomena in ultra-deep formation of East China Sea Shelf Basin (ECSSB). To address this, the pore pressure distributions in the ECSSB are characterized in detail, utilizing measured pressures, mud weights, and logging responses. The genesis mechanism of PPS and PPR in ultra-deep formations is investigated. Finally, the significance of unveiling the genesis mechanisms behind PPACs to pore pressure prediction is discussed. The results indicate that the pore pressure in the ultra-deep formation is complex and variable, with the middle pressure rapidly rising to 1.8 and the lower formation reversing to 1.0, characterized by a reducing return trend. The primary cause of these PPACs is identified as the significant variation in overpressure mechanisms and lithological characteristics across different layer. Hydrocarbon generation serves as the primary mechanism for pressure formation leading to a surge, followed by pressure transfer. Furthermore, a multi-source and multi-mechanism pore pressure prediction model suitable for ultra-deep PPAC formation is established. It takes into account the influence of multiple factors such as composite overpressure mechanism, complex lithology, rock mechanical properties, rock conduction properties and rock volume properties. The results demonstrate that this novel model exhibits good applicability and reliability, with the prediction error margin controlled below 5.00% and an average error of just 2.23%. This research provides novel insights for understanding the genesis mechanisms behind PPACs and predicting pore pressures in ultra-deep formations.