Abstract: The experimental system for laser-induced acoustic signals has been built. Acoustic signals are induced by pulsed laser focusing into water. A hydrophone is used to convert the acoustic signals into electric signals. The mathematic model for laser-induced acoustic signals in time and frequency domain has been analyzed. The energy distribution of the laser-induced acoustic signals in frequency domain has been studied. Characteristics of spectrums of acoustic signals produced by lasers in different repetition rates have been analyzed through experiments. The results are as follows: the laser-induced acoustic signals have most of their energy concentrated before 200 kHz, where half of that is between 100 kHz and 200 kHz. The maxima of laser-induced acoustic signals in frequency domain can be controlled by repetition rates of lasers.