Abstract: Compartmentalized overpressured systems are commonly developed in tight gas sandstones. However, studies about the characteristics of overpressure regime in compartmentalized overpressured system are rarely reported in the literature. The Upper Triassic Xujiahe tight sandstone formation in the Yuanba-Tongnanba area, northeastern Sichuan Basin, is a typical compartmentalized overpressured system. In this study, an overpressure regime in a compartmentalized overpressured system was delineated based on abundant measured pressure data, and the factors controlling overpressure regime in the compartmentalized overpressured system were clarified by comprehensively analyzing the geologic and geochemical data and the structural evolution of source rocks and tight sandstones. Results show that the overpressure regime in the compartmentalized overpressured system within tight sandstones of the Xujiahe Formation were separated from each other in both vertical and horizontal distribution of sandstone intervals, or even in the same intervals, exhibiting multi-scale and multi-level features for the compartmentalized overpressured system. Natural gas filling is a primary dynamic cause for overpressure generation, and its magnitude is directly related to gas generation intensity. The generally densified sandstones formed the background of overpressure system. Locally distributed mudstones and mudstone interbeds, and highly densified sandstone interbeds formed a multi-scale and multi-level framework of the overpressure system.