A detailed finite element analysis is presented in this paper in order to obtain the different vibration properties of two kinds of fixed jacket platforms under wave force. More attention is paid to the platform with prism shape jacket because of its more possibly excessive vibration in service than that of the jacket platform with slant piles. Numerical simulations are compared with the results from actual platform test and an effective strengthening technique is proposed. The conclusion of the paper may be taken as the basis of following control work.It also gives some guidance to the future design of the fixed platform with prism shape jacket.