Abstract: The research on the vocalization and signal characteristics of bottlenose dolphins in natural environment has been done.A large amount of original vocal signals are obtained by the broad frequency-band recording system integrated by laboratory instruments.Signals are evaluated by Matlab tools,and the results suggest that the sounds of bottlenose dolphins are complex and diverse,mainly including click,whistles and burst pulses etc.The paper focuses on the clicks having high frequency and narrow time.Clicks have a wide range of frequency distribution concentrating in 2～160 kHz and the peak frequency as high as 110 kHz,but dolphins in tank emit clicks with lower peak frequencies.The number of clicks is obviously different under different acoustic behavior.Dolphins emit clicks more frequently at feeding and training times but the trends of spectral characteristic variation are basically the same.