The invention provides an underwater target sound wave detection method and a device based on coherent laser. The method comprises steps: S1, detection light after water surface sound wave modulationand scattering is acquired, and interference with reference light is carried out to obtain water surface wave interference signals; S2, based on an approximate global optimization principle of a simulated annealing algorithm, wavelet ridges of the water surface wave interference signals are extracted though a ridge recognition method; and S3, the frequency of the water surface sound wave is obtained according to the central scale of the wavelet ridges. Through carrying out interference on the detection light carrying water surface microwave signals and the reference light, the interference waves are analyzed and processed based on the wavelet ridge extraction method of the simulated annealing algorithm, accurate extraction on the signal frequency during an underwater sound signal extraction process in a laser interference method is realized, and influences on the measurement precision by environment noise can be reduced to a great extent.