Abstract: The dynamic equations of the coaxial two-body wave energy converter（WEC）are established in this paper. The optimal damping coefficient and the maximum output power under linear PTO damping force are solved by theoretical analysis. A new method of estimating the maximum power is presented. The results show that the two-body WEC can maximize the energy capture by adjusting the PTO damping,which widens the energy capture frequency band width compared with the single-body WEC and has better energy capture performance in specific sea areas. What’s more,the effect of the control strategies and viscous damping force has also investigated.