When high-power laser is focused in water through an optical focusing lens system, the water is broken down and high-power acoustic wave is emitted. The different optical focusing lens system relates to different acoustic waveform characteristic, such as the sound pressure intensity, frequency. In order to analyze the relation between the pressure signal and optical focusing characteristic, we simulate the dynamic process of the laser-induced cavitation bubble model and the laser-induced acoustic signal model. The experimental investigation is done. The laser-induced pressure acoustic signal is detected with the high-frequency transducer. The laser-induced cavitation bubble expansion and collapse is recorded with high-speed video. The shock wave and cavitation bubble begin after optical breakdown in water. The laser-induced bubble radius and power acoustic density make a linear relation with the laser energy directly. For high-power laser, compared with the unexpanded beam, the bumble radius is larger and the acoustic signal is more intense for the expanded beam. To increase the opto-acoustic efficiency, the laser beam should be expanded and focused.