The survivability of wave energy converter(WEC) in extreme sea conditions is key index that affects its overall performance. In this paper, CFD method is used to simulate the response of a cylindrical WEC in waves. The naoe-FOAM-SJTU solver based on the open source CDF platform OpenFOAM is used for the simulation. Focused waves of certain amplitude and period are generated using Waves2Foam solver, and the accuracy of the waves is verified through comparison with experiments. The interaction between the fixed cylinder and floating cylinder with the focused wave is simulated respectively, then the pressure and force of the cylinder together with surface elevation are analysed. The results show that the influence of cylinder motion on surface elevation is significant. The change of wave pressure on the fixed cylinder is more likely to cause damage to the structure. The interaction between the cylinder and the wave affects the amplitude and period of the force on the floating body.