Deep sea cages are an important part of fishery equipment and play an important role in modern fishery. A self-elevating cage is a special form of a deep-sea cage. In actual production, it can quickly sink to a deeper position below the water surface by various means when a typhoon or red tide comes so as to resist the adverse effects of complex sea conditions. This study carried out the hydrodynamic performance of the self-elevating cage and its supporting system to explore the hydrodynamic factors affecting the self-elevating cage, optimize and improve the cage structure, reduce the loss of cultured fish in extreme working environments, and improve the safety of the cage system. In this study, the effects of different flow rates, different inflow angles, different dive depths, and different types of netting on the stress of steel structure self-elevating cages were investigated through physical model experiments. The results showed that when the mesh size, the diving depth, and the inflow angle were the same, the overall force of the self-elevating cage was positively correlated with the water flow velocity. When the cage was perpendicular to the water flow direction, the force of the cage was the smallest, and the inflow angle of the cage might be subjected to the maximum impact force at 30 °-60 °. The force of the model cage at 50 cm from the water bottom was greater than that of the cage at 80 cm from the water bottom. The stress of UHMWPE netting was larger than that of PET netting with the same line area. The results showed that the hexagonal mesh PET net could be preferred in the cage design, and the attachment could increase the force of the net to more than 10 times the original. It was suggested that the influence of the attachment on the structural strength of the cage should be fully considered in the design of the cage structure. This study can provide a reference for the design, layout, and netting selection of self-elevating cages. As a kind of deep-sea aquaculture equipment, the prospect of a self-elevating cage is extensive, but the related work has a long way to go.