According to the principle of ultrasonic distance measurement and target determination, Combine Wifi technology with mobile APP and hardware to design a portable fish retrieval system for recreation. First, the transmission and control of the ultrasonic transducer signal and the acquisition of the target echo signal are realized by using the integrated chip CC2500.Second, According to the echo information and the threshold detection algorithm, we can calculate the distance between the fish and the fish，and A / D sampling data from the selfformat format package. Finally, it is sent to the smartphone through Wifi. The test results show that the fish exploration system can determine the target according to the echo signal, and clearly presented in the mobile application interface.