Abstract: A quantitative simulation method for contributions of three origin of overpressure in sandstone is provided. Analytical testing data, well logging data, geological data, seismic data, and the like are collected and collated. A formation pressure characteristic of sandstone of a target horizon is analyzed and a burial history and a thermal history of the sandstone of the target horizon is reconstructed. An undercompacted pore pressure evolution history and an undercompacted hydrocarbon generation pressurized pore pressure evolution history, and a total pore pressure evolution history is quantitatively simulated. A quantitative analysis is performed on contributions of three origin of overpressure: quantitatively analyzing contributions of undercompaction, pressurization by hydrocarbon generation, and other origin to overpressure according to Ptotal=Punderc+Phydrog and Ptotal=Punderc+Phydrog+Ptotal to obtain overpressure evolution mechanisms of three origins.