Nowadays, wave energy plays an important role in renewable energy resource. In over 30 years, several researches in wave energy converter system (WEC) have been deployed and carried out. This paper proposes a new mechanism to achieve the resonant behavior of a point absorber floating buoy type of WEC system with mechanical power take-off. The original WEC system uses the bidirectional gearbox to convert up and down motion of the wave in heave mode to one-way rotation. By designing the array of hydraulic springs, the equivalent stiffness of the float can be reduced to close to the relatively low frequency of the wave. Then the buoy is at near resonance with the wave, also increase the power capture bandwidth and the performance of the operating system. In this paper, the specification of the system is proposed and studied. The working principle is analyzed. The mathematical model is then derived to investigate the operation. Experiments are performed to validate the simulation results based on mathematical model. Numerical simulation using Matlab/Simulink has been done to evaluate the effectiveness of the new control stiffness mechanism.