A calibration method includes: (S1) generating an external light path via a laser automatic power control circuit through a high frequency modulation signal, sending the external light path to a measured target, reflecting the external light path back through the measured target and receiving the reflected external light path by a photoelectric receiving circuit; (S2) generating an internal light path via the laser automatic power control circuit through the high frequency modulation signal, directly sending the internal light path to the photoelectric receiving circuit, and receiving the internal light path through the photoelectric receiving circuit; and (S3) performing phase comparison between two paths of light waves respectively corresponding to the external light path and the internal light path received firstly and secondly by the photoelectric receiving circuit, and a reference phase signal through the photoelectric receiving circuit, calculating a distance phase, and outputting a signal whose base is eliminated.