Gubei sag has abundant hydrocarbon resources，and the overpressure zones are widely developed in this area.According to the drilling stem test data，present-day overpressure commonly occurs at the depth ranging from 2 800 to 3 800 m. As the sonic transit times have obvious responses to overpressure in both sandstone and mudstone with similar range of variation and trend，the Eaton method was used to predict overpressure in sandstone reservoir. In addition，the distribution characteristics and the controlling factors of the pressure distribution were analyzed combining the drilling stem test data. On the whole，two overpressure systems were identified in the vertical including an upper system distributed in lower Ed and Es1 and a lower system in Es3 and Es4 which is also the main overpressure zone. In plane，overpressure distributes in the east and the west subsags，and it decreases gradually from the center to the uplift and boundary faults. The distribution pattern of reservoir overpressure is mainly influenced by faulting，mudstone thickness and content and hydrocarbon generation of source rock.