It is an important work to study the hydrodynamic characteristics of the net structure to guarantee the safety of the whole net cage system in deep open sea. The most widely used copper alloy net in aquaculture cages is of the “chain-link” type mental net, which is a kind of porous structure with a small diameter, whose hydrodynamic characteristics under the waves and currents is significantly different from general ocean engineering structures. Based on the finite element method, the chain-link nets and the interaction between them are simulated by the beam element and connector element in the ABAQUS software. After verification by the experiment data, the different flow resistances on the net under currents with different net diameters and mesh sizes were analyzed. The numerical simulation results showed that as the mesh size increases from 25mm, 35mm to 45mm, the average value of the flow resistance increases with the amplification of 14.71% and 38.07% respectively under various operating modes. Similarly, the average value of flow resistance increases with the amplification of 25.05% and 45.06% respectively under various operating modes as the net diameter increases from 2.5mm, 3.2mm to 4.0mm. The research provides a positive foundation for further study of the hydrodynamic characteristics of deep-sea aquaculture metal cages.