Abstract: An experiment system for laser-induced acoustic signal has been built. Acoustic signal is induced by pulse laser focused into water. A hydrophone is used to receive and convert acoustic signal into electric signal. The energy of the acoustic signal is calculated. Laser acoustic energy conversion efficiency is theoretically and experimentally analyzed. The results are as follows: as laser energy increases, energy conversion efficiency decreases; the longer distance the laser travels before being focused, the smaller the energy conversion efficiency is; energy conversion efficiency increases as absorbed energy by plasma increases; water salinity has little influence on energy conversion efficiency.