Abstract:In order to obtain the acoustic characteristics of the jellyfish(Aurelia aurita) at different frequencies, the Target Strength (TS) measurement experiment was carried out on the jellyfish with an echosounder in the pool. The results showed when the attitude angle of the jellyfish was 60 °~90 ° and the bell diameter was about 10 cm, the measured value of the TS was - 66~- 63dB at 120 kHz, which was close to the high flux liquid sphere model, and the measured value of the TS was - 61~- 59dB in the frequency band of 90~170kHz, which was close to the Mutlu bell-diameter model. In addition, the reasons for the differences in the measured TS of the jellyfish with the same bell diameter were given. The conclusion of this thesis will provide a reference for nuclear power plants to conduct a detection of cold source disaster causing organisms in shallow sea with a broadband echosounder.