The invention discloses a method for detecting and inhibiting direct-current component of soft hardware. According to the method, in DSP (Digital Signal Processing) digital control PWM (Pulse-Width Modulation), the output pulse width of a digital circuit is acquired by digital comparison of modulation wave and triangular wave, therefore an integral (including positive negative pulse) of PWM output voltage in an industrial frequency period is calculated by detection, and if the integral is zero, the modulation waveform emitted by a controller can be considered symmetrical, otherwise, direct-current component is considered to be generated and the corresponding direct-current component is eliminated by a software compensation method. Because sampling is performed once per a certain period in a digital controller, as long as the modulation wave in one industrial frequency period is accumulated in each industrial frequency period and ensured to be zero, the direct-current component can be ensured to be zero, and if the accumulated sum is not zero, the value is used as the offset of the modulated quantity for the next industrial frequency period, thereby ensuring that the direct-current component is zero.