Underwater submersibles operating in emergency conditions are susceptible to ferromagnetic interference from the mother ship, leading to degraded positioning accuracy. To address this issue, a positioning error correction method for underwater submersibles based on reverse attitude update is proposed. When initial magnetic interference exists, the method first performs inertial navigation and stores the raw data. After the submersible detaches from the mother ship and the magnetic signal returns to normal, it recursively recalculates and corrects the original initial attitude angle using the inertial-phase data and reverse attitude update algorithm. Subsequently, inertial navigation and integrated navigation are re-executed with the revised initial attitude angle to eliminate the systematic errors induced by the original initial attitude angle. This method enables the estimation and compensation of both initial and process errors by leveraging the later-stage integrated navigation results. Experimental results demonstrate that, compared with the traditional integrated navigation method, after compensating for the initial heading and horizontal attitude errors of the submersible, the average position error during navigation is reduced by 87.8% and the average velocity error by 91.3%, which significantly improves the positioning performance of the integrated navigation system for underwater submersibles in emergency scenarios.