A range-gated underwater imaging system is designed for solving the problems in detection in shallow waters. The system is built around a pulsed 532 nm NdYAG laser and a self-made gated intensified charge-coupled device (ICCD) camera, and the laser pulse is used as the trigger for sync control of the system. The camera gating is timed to collect light reflected from the target to produce the target in the image. The range-gated underwater laser imaging experiment is done based on the sync control circuit designed by field programmable gate array (FPGA) technology. The experimental results indicate that the laser pulse jitter can be restrained by using laser pulse as trigger. As a result, water surface reflection and water backscattering are eliminated effectively and the imaging quality is enhanced. It is also proved that the imaging depth of the system is 7 m in the lake whose effective attenuation coefficient is 0.52 m-1, and the target can be effectively detected and recognized in shallow waters.