The invention relates to an output voltage regulating circuit for a buck switch power converter. The invention aims at the problems that the gain of an error amplifier is reduced and that the requirement on a load regulation rate cannot be met in the prior art, and provides a power converter for regulating output voltage by employing digital technology. The technical scheme is that: the power converter with digital calibration function comprises a control logic unit, an error amplifier, a pulse-width modulation (PWM) comparator, a driving unit and an output unit, and is characterized by also comprising a digital control unit, wherein an input end of the digital control unit is connected with output voltage and an output end of the digital control unit is connected with error voltage; and when the output voltage exceeds a preset range, the digital control unit changes the amplitude of the error voltage in a stepping mode, so that the output voltage is kept in the preset range. The digital calibration circuit can be applied to a nano process and has wide using prospect for the power converter made by a traditional process.