Abstract: The experimental research on acoustic signals of the south sea. lion(Otoriabyronia) is conducted for determinig. its ability of echo rarlging. It is found that underwater acoustic signals of the souther sea lion can be grouped under two heads on the whole. On P is long duration signals-whistles, and its average duration is from several tens of millisecond to one seconds anothex. one is pulse trains clicks, and its average duration is about 3.6 inillisecond.,The sound production of the sea lion is closely related to its behaxiour. Swimming in free state, the sea lion emits less acoustic signals and most of them are Whistles. When the living, fish are thrown into the water, the sea lion follows up the fish very fast until all fish are swallowed and emits pulse trains simultaneously.When the fish are thrown in the dark, the pulse changes vary obviously, the,pulse amplitude increases 3-5 times, the pulse duration shortens, and the frequency of pulse rises.These changes are due to the needs of echo-ranging and tracking the living fish in the dark. We may come to the conclusion that the south sea lion has the ability of echo-ranging. In this paper, the typical waveforms and spectra of underwater sound signals of the south sea lion are presented.The experiment shows that the high threshold value of the audible frequency of the south sea lion is about 90 kHz.