The conservation of cetaceans in Pescadores was originated in 1990. However, the conflict between the fishery loss and cetacean protection keeps growing. The fishery loss caused by cetaceans are mainly: “steal fish” and ”frighten fish group”, and the others like ”damage fishing gear” and ”interfere fishing operation”, and etc.By the understanding of dolphins behavior, this study proposed acoustical deterrent methods; 1.harassment:look for echolocation system frequency range, and broadcast disarrange signals to produce an illusion, and prevent dolphins from locating the target. 2. threat: broadcast sounds of its predators which is killer whales to scare dolphins from approaching the fishing vessels. 3. warning: loud noise or alert sounds of dolphins. The circuits of generating above sounds are designed, test and modified after the field test . Underwater speaker was used to broadcast sounds of 10 kHz , 20 kHz , killer whales sound and distress call of dolphins. The test results showed these dolphins avoided the sound source, especially during killer whales sound and stress call of dolphins. They were effective to deter dolphins to reduce stealing fish on the sea. More effective deterrence device should be developed through this study to reduce the loss of fisherman, and achieve the cetacean conservation goal.