For the design of the underwater laser detection system, the echo power equation of underwater target is derived, and the effects of water’s attenuation coefficient and incident angle on target’s echo power are analyzed. The bidirectional reflection distribution function (BRDF) of the single-station model is used to study the reflection characteristics of the target. The influence of the correlation coefficients of specular and diffuse reflection components on the reflected light intensity of special axisymmetric targets is studied. The signal-to-noise ratio (SNR) values of three types of target under different surface BRDF are given. The simulation results show that the larger the attenuation coefficient is, the smaller the echo power received, and the incidence angle is closer to 90°, the echo power is equal to 0. A smaller surface slope or a larger diffuse reflected coefficient will cause a smaller reflected intensity.