The invention relates to a detection system, in particular to a capacitor bank fault detection system. The capacitor bank fault detection system comprises a power source input interface and a voltage sampling interface. The power source input interface is connected with a three-phase voltage regulator and capacitors to be tested, connected with a current mutual inductor and a voltage mutual inductor and used for converting the current and the voltage of the capacitors to be tested. The obtained current measuring signals and the voltage measuring signals are converted to digital current signals and digital voltage signals through an analog-digital converter and sent to a processor after passing through a current signal adjusting circuit and a voltage signal adjusting circuit. The processor obtains the capacitance value according to the digital current signal, the digital voltage signal and a phase angle between the digital current signal and the digital voltage signal. The voltage sampling interface obtains the measuring voltage on the secondary side of a discharging coil and sends the measuring voltage to the processor after converting the measuring voltage through the analog-digital converter. The capacitor bank fault detection system can measure the single-phase capacitance of a parallel connection capacitor bank and measure three-phase capacitors of various connection types at the same time without detaching wires, and detection is simple and efficient.