Cage culture facilities that used for the purpose of fish farming are inatalled in the coastal or offshore, which exposed to a variety of marine environments. Fish cage mainly consist of frame part, net, and mooring system. Among them, the behavior of the frame part affects the survival and growth of fish. In addition, at break of the frame can be great damage such as loss of fish. Therefore, to understand the mechanical behavior of the cage frame is important step before design of cage system. In this study, we carried out numerical simulation to get dynamic response of a square cage under wave forces. In addition, the structural stability was investigated by performing static analysis of the frame.