Based on the potential flow theory, a two-dimension mathematical model of oscillating water column (OWC) wave energy device was obtained. The fully nonlinear wave was simulated in the desigularized boundary integral equation method (DBIEM). The anti-reflection was achieved by adjusting the amplitude and phase of the oscillating air pressure in the OWC's chamber. The relationship of the wave energy absorption efficiency with the amplitude and phase of the oscillating air pressure in the OWC's chamber was investigated. Numerical results have shown that the wave energy absorption efficiency of OWC at anti-reflection is much higher than that of the traditional OWC. Under the condition of anti-reflection, the amplitudes of the oscillating air pressure in the chamber and the flow through the turbine are much higher, and the phase differences between the two are observed, which differ from the traditional OWC. A novel design idea of the OWC wave energy device was also presented.