Based on the working environment of the cage, the gravity marine aquaculture cage system was taken as the research object. The ocean floating platform and the cage hydrodynamic simulation model was established by means of the mesh grouping. The lumped mass method and Morison equation were applied to studying stress distribution and deformation of cage system with the motion response of aquaculture floating platform under wave and flow load. Then, the credibility of the research method was verified by comparing with the experimental data. The results show that the mooring line fluctuated greatly under the action of wave and current; the most stressed area of the net appeared near the mooring line, and the maximum tension of horizontal rope in the most stressed area was 4.8 times smaller than that in adjacent vertical direction; in addition, the deformation of the cage was mainly affected by wave and current and changed reciprocally; in particular, the minimum the net volume reduction coefficient was 80.1%; moreover, as the increase of the sea state, the mooring line tension increased and the net volume reduction coefficient decreased and the minimum net volume reduction coefficient was 60.5% in sea state 6. The research results can provide technical support for the application of the gravity marine aquaculture cage systems.