A new method has been developed to detect real-time underwater acoustic signals with laser and a corresponding test system has been built.The experiment results prove that the method can be used to detect real-time underwater acoustic signals with a frequency between 1 kHz to 14 kHz.This test system consists of an underwater acoustic source,a precise optical detection device,and data acquisition and processing components.When the underwater acoustic source generates sound causing fluctuation of the water surface,let laser beams irradiate the water interface from air,and the scattered light will carry frequency information of the acoustic waves.The precise optical detection device adopting basic principle of Michelson interferometer can detect change of optical parth difference caused by the water surface fluctuation,and achieve real-time information concerning audible frequency of the underwater acoustic source in the data processing system by means of demodulation.This completely innovative method provides a novel technical solution for aerial remote sensing of underwater objects.