The invention discloses a digital laser phase-locking device, which mainly comprises the components of a laser, a beam splitter, a photodetector, a biased junction, a directional coupler, an amplifier, an integrated phase-locked loop frequency synthesizer, an external reference source, a digital PID control module, a computer and the line, wherein the components are connected with a circuit through optical paths to form a whole body of the digitalized laser phase-locking device, and an electrical phase-locked loop is expanded to a laser frequency to lock the phase of the digitalized laser phase-locking device. The digitalized laser phase-locking device adopts the integrated phase-locked loop frequency synthesizer to ensure that controlled difference frequencies are different from one another from dozens of trillions to 7 GHz; the digital PID control module is used for realizing that a computer controls the phase-locking process, adjusts the parameters of the digital PID control module and changes the phase-locking position; and the operation is convenient, the optical paths are simple, and only one beat frequency optical path is needed.