Based on the velocity invariability of the shallow water wave and using the shoaling effect,a unique active wave absorber for numerical wave tank is set up. This absorber’s absorption parameter is constant there by make its mechanism very sinple When coupled with damping zone, it can achieve a Perfectwave absorption effect By setting different absorption parameters and coupling with a damping zone 4 ISOPE wave absorption benchmark experiments are perforned using this absorber The results indicate that by setting shoaling bottom this absorber has excellent absorbency on deep water waves and limit depth waves and when coupled with damping zone it not only can absorb the wide spectrum nonlinear random waves but also shorten the length Of the damping zone effectively.