As China’s maritime industry expands, efficient and safe handling of cargo within the constrained spaces of ship cabins is crucial for reducing operational costs and enhancing safety. This paper introduces a control algorithm based on a programmable logic controller (PLC) for a marine mechanical arm designed to optimize cargo transfer operations aboard ships. Utilizing electric motor-driven arms controlled through ST language and ladder diagrams, the system allows precise cargo handling by following operator-guided paths and effectively circumventing obstacles within the confined space. Experimental evaluations demonstrated significant improvements in operational efficiency, with the mechanical arm successfully navigating complex cabin layouts. There was a 90% reduction in manual intervention and a 20% increase in cargo transfer speed under dynamic sea conditions. This innovative algorithm not only enhances operational safety by maintaining cargo stability during ship movements but also serves as a scalable solution to meet the evolving demands of modern maritime logistics operations.