Based on the theory of thermally expanded laser-induced acoustic phenomena, the relationship between laser parameters and the underwater acoustic pressure and directivity of laser-induced sound wave was analyzed, including the laser pulse width, beam radius, pulse energy, pulse waveform, and laser wavelength. The results indicate that under the thermal expansion mechanism, 1064 nm Nd: YAG and 10.6 μm CO? lasers serve as relatively ideal excitation sources. Before approaching the vaporization threshold, the sound pressure generated by laser-induced acoustic effects is proportional to the laser power density. Reducing the laser pulse width suppresses the size of side lobes effectively, thereby improving the directivity of the acoustic pulse, but simultaneously increases the frequency and bandwidth of the acoustic signal. Increasing the laser spot radius can suppress side lobe size while compressing the acoustic signal bandwidth and reducing high-frequency components; employing a flat-top laser pulse waveform generates narrower acoustic pulses, facilitating detection of smaller underwater targets. Building upon this, the propagation distance of acoustic waves in seawater under thermal expansion mechanisms was analyzed and evaluated by integrating studies on acoustic transmission loss characteristics in seawater. Using a 1064 nm laser source with 1 J pulse energy, 1 μs pulse width, and 1 cm spot radius, the underwater acoustic wave generated by thermal expansion can propagate approximately 27 meters. Increasing both laser pulse energy and spot size while maintaining constant peak power density achieves a transmission distance of 100 meters, requiring 33 J pulse energy and a 5.74 cm spot radius. With a 10.6 μm laser with 0.5 J pulse energy, 500 ns pulse width, and 1 cm spot radius as the excitation source, the underwater acoustic wave transmission distance reached 45 meters. To achieve a transmission distance of 100 meters while maintaining constant peak power density, the required pulse energy and spot radius were 8 J and 4 cm, respectively.