Abstract: The Shaximiao Formation, located in the central-western Sichuan, is a tight sandstone gas reservoir with a complex rock composition, low porosity, and complex structure. Due to tectonic movements, multiple pressure systems coexist, resulting in significant variation in the formation pressure between different sand bodies vertically and horizontally. A classification formation pressure prediction method was proposed to address this issue. According to the measured formation pressure data, the vertical pressure unit was divided based on the Shaker division and we used parameters such as vertical depth, resistivity, porosity, three-porosity ratio, and gas saturation to analyze the correlation between each parameter and the formation pressure coefficient. Based on this classification, a comprehensive pressure index chart was constructed to predict the formation pressure. There are two types of charts: ultra-low-pressure charts and normal- and low-pressure charts. An ultra-low-pressure chart established by the comprehensive pressure index and vertical depth was used to determine whether the pressure type was ultralow, and the model established by the water absorption principle of the underlying mudstone was used to predict ultralow pressure. The pressure of this type is predicted according to the Eaton method, selected after comparing and predicting normal and low pressures using the Eaton, Fillippone logging, and effective stress methods. The model was based on the principle of water absorption of the underlying mudstone for predicting the ultralow pressure. The coincidence rate of chart classification reached 85%, and the overall prediction result of the formation pressure coefficient was as high as 96.15%. This outcome is consistent with the measured results and provides a calibration basis for the vertical divisional classification calculation of the formation pressure of the Shaximiao Formation and the prediction of seismic formation pressure.