The invention relates to a fault detection method, device, system and equipment of a filter capacitor. The fault detection method of the filter capacitor comprises the following steps: obtaining phasevoltage and phase current of a three-phase filter capacitor; calculating a positive-sequence phase voltage and a negative-sequence phase voltage corresponding to the phase voltage and a positive-sequence phase current and a negative-sequence phase current corresponding to the phase current by an extraction symmetric component method according to the phase voltage and the phase current; calculating the equivalent conductance of the three-phase filter capacitor through a first conductance coefficient matrix according to the positive sequence phase voltage, the negative sequence phase voltage, the positive sequence phase current and the negative sequence phase current; and determining the fault state of the three-phase filter capacitor according to the equivalent conductance. According to the method, impedance asymmetry detection is performed based on phase voltage and phase current data of the three-phase filter capacitor, and equivalent conductance is determined to detect a very smallline current change, so that the very small impedance change can be detected to accurately sense whether the three-phase filter capacitor is subjected to a fault.