Abstract: The fish cage in sea is affected by the hydrostatic effects and hydrodynamic effects. To ensure the safety of net cage system, it is necessary to carry out transient dynamic analysis. Therefore a finite element method is employed to determine the dynamical response of the fish cage. The fish net deformation and mooring line force are simulated for the cage in current and wave, and then the simulation results are compared with the experimental results. The results show that the method has good accuracy as compared with the measured results of physical modeling test in the wave-current flume. The computer simulation reveals the dynamical response characteristics of the fish cage in current and wave well.