When a manned submersible fails to surface in an emergency, the emergency buoy acts as the final safeguard, establishing a connection between the submersible and the rescue vessel on the surface, providing both position indication and a tow line for subsequent rescue operations. The rationality and effectiveness of the emergency buoy design are particularly critical. In this paper, a mathematical model of the cable of emergency buoy rescue system is established, and the cable shape and tension distribution of the emergency buoy rescue system of manned submersible under different working conditions are calculated and analyzed. The variation patterns of cable shape and tension are obtained for different deployment depths of the emergency buoy, different net buoyancies, and different cable diameters. This study can provide a reference for the design of manned submersibles.