A research on laser coherent detection is developed to detect underwater acoustic signals in different frequencies and vibration intensities under laboratory conditions. And an experiment system is established based on the research. A beam of laser is irradiated water surface when the water surface is fluctuated by underwater acoustic signals. The generated scattering light with acoustic wave information will interfere with reference light. Interference signals are collected and processed to obtain the frequency and intensity information of underwater acoustic signals. Experimental results obtained under different conditions are compared and analyzed. The results show that underwater acoustic signal can be detected effectively with laser interference detection technology. And detection effects become weaker with the increasing of frequency and the weakening intensity of signals. Full fiber path design is used in the experimental system and better effect is got.