With the aim of studying the characteristics of laser-triggered surface flashover in voltage pulse, synchronization problem of laser pulse and voltage pulse should be solved. Of the laser-triggered surface flashover facilities, a high precision laser trigger system is built up. A single/double harmonic, with wavelength λ of 1064/532 nm, Q-switched Nd:YAG laser is used to trigger the surface flashover. The synchronization problem is solved using a self-made digital delay/pulse generator. The delay time and jitter of Marx's trigger input and output, Marx's trigger output and Marx's output, laser input and output are respectively measured. Based on the result of the delay time and the timing sequence of the laser triggering system, digital delay/pulse generator controls Marx's trigger and the Xe lamp of laser, and the Q-switch of laser is controlled by the Marx's output. The synchronization of laser pulse and voltage pulse is obtained through adjusting the channel delay time of digital delay/pulse generator.