The Ordos Basin's marine carbonate reservoirs often experience downhole complexities such as gas invasion, lost circulation, and borehole collapse during drilling. It is particularly important to systematically evaluate the overpressure mechanisms and accurately predict formation pressure for the exploration and development of the target strata. The carbonate reservoir of the Ordovician Majiagou Formation in the eastern Ordos Basin was selected as the research target. Overpressure mechanisms were analyzed using the combination of well log curve analysis, effective stress-acoustic velocity method, acoustic velocity-density method, and comprehensive analysis method. A physical model of elastic modulus for carbonate rock matrix, framework, mixed pore fluid, and saturated fluid rock was established, and combined with the effective stress principle, a method for predicting formation pressure was developed, applicable to the Majiagou Formation in the eastern Ordos Basin. Finally, the model's accuracy was verified using field data. The results indicate that hydrocarbon generation is the primary cause of overpressure in the target reservoir, with undercompaction and structural compression as secondary factors. The new model achieves a relative error of less than 10%, demonstrating strong applicability and high predictive accuracy. The research results provide guidance for the study of hydrocarbon accumulation in the Majiagou Formation in the eastern Ordos Basin.