The paper discusses the detection and cognition of the laser echo signal of underwater target, based on the ability of the Gabor expansion to localize signals. In virtue of the multiple correlation analysis for the expansion coefficient in local window, the detection method of peak value is founded. By taking the trace and characteristic value of the coefficient matrix as parameters to describe the reflecting ability of underwater target, the classified cognition of the target is carried out. Experimental results show that the effective target detection probability is 93.0% and the classified recognition probability is 83.2%.