Single-photon imaging technique is a new type of light detection and ranging (LIDAR) technology used for weak signal detection which has a high sensitivity up to single-photon energy level. It has a broad prospect of application in the field of underwater imaging. Range-gated technique has been proved to be effective in reducing the backscattering noise and improving the signal-to-noise ratio (SNR) during the data acquisition stage. The range-gated synchronous control system is a key component of the underwater single-photon imaging system. At present, most range-gated synchronous control systems have the defects of low stepping regulation precision and narrow dynamic regulating range. This paper designs a novel range-gated synchronous control system which has both a wide dynamic regulating range and a high stepping regulation precision of gating distance. It is composed of a coarse regulation part and a fine regulation part which are both based on the field programmable gate array (FPGA). The simulation results show that the dynamic range of the system’s gated distance can meet the requirement of imaging as far as 7km, and the stepping regulation precision can reach as high as 39ps, with the gate width adjustable. The system designed in this paper guarantees a high SNR data acquisition and has a strong adaptability under various distance scenarios along with extra advantages of lower cost, smaller volume and lighter weight. These features will make a great improvement in the crypticity and portability of the whole underwater single-photon imaging system. © 2021 SPIE.