A flyback converter and an output voltage acquisition method therefor and apparatus thereof, wherein the output voltage acquisition method comprises the following steps: acquiring the reference output voltage of a flyback converter; sampling the current output voltage of the flyback converter within a reset time of each switching period among M continuous switching periods of the flyback converter, wherein M is a positive integer; and according to the reference output voltage and the current output voltage, sampling a dichotomy to successively approximate the current output voltage until the M switching periods are finished, and acquiring the output voltage of the flyback converter.