A method for calibrating frequency, applicable to calibrating a frequency signal generated by a frequency generating unit of an apparatus at a preset frequency, includes obtaining the cycle number of the clock rate of a frequency signal based on a reference signal and a clock mask synchronous with the frequency signal; obtaining a frequency of the frequency signal based on the cycle number; correcting the frequency according to a plurality of phase shift signals generated based on the reference signal; and minimizing an error of the frequency of the frequency signal by increasing the quantity of the phase shift signals, so as to calibrate the frequency signal generated by the frequency generating unit.