ing at the problem of locking the long-term frequency drift of a laser, a digital laser frequency stabilization system is achieved with reference to an optical frequency comb. In this system, the heterodyne interference between the slave laser and the optical frequency comb is first performed to obtain the beat signal which represents the laser frequency drift. Then, the frequency of the beat signal is measured by a self-developed digital-counting-based frequency to voltage conversion circuit, and the value of the measured frequency is converted to an error voltage signal. At last, the slave laser is controlled through the feedback control of the master program. In the long-term frequency stabilization experiment of a 760 nm narrow linewidth semiconductor laser, the system improves the long-term stability of the laser frequency by two orders of magnitude, and the stability of the laser reaches 4.4×10 ^-10(τ=262 s). Experimental result shows that the proposed system can achieve a long-term frequency drift locking for lasers with wavelength locating in the spectrum range of the optical frequency comb. This system can provide a basis for further fine-locking of the frequency and phase of the laser.