Embodiments of a distance measurement system are provided, in which a light signal generator comprises a first emission unit outputting a light beam to a target according to a first frequency-modulation signal, and a light-mixing unit generating a light mixing signal according to a second frequency-modulated signal and a reflection light beam reflected from the target. An electrical mixing unit generates an electrical mixing signal according to the first and second frequency-modulation signals, and a processing unit performs a phase difference estimation to obtain an evaluated value between the target and the distance measurement system according to the light mixing signal and the electrical mixing signal, and obtains a corresponding distance compensation value to compensate for the distance evaluated value according to an amplitude of the reflection light beam.