In this study, a compact magnetic bistable mechanism is proposed to enhance the efficiency of a point wave energy converter (WEC) with a linear damper like Power Take-off (PTO) system. The magnetic bistable mechanism mainly consists of two coaxial permanent magnet rings with the same magnetic field direction. The dynamic model in the time domain for the nonlinear point absorber is established by using the state space method to replace the convolution term. The wave energy capture characteristics are analyzed in regular and irregular waves. The numerical results show that the magnetic bistable mechanism can shift the frequency bandwidth of the point wave absorber to the lower frequency which covers the realistic wave excitation frequencies in regular wave. The efficiency for the bistable WEC with large inter-well oscillations can be enhanced by about two times comparing with that of a classical linear WEC in irregular waves.