The invention discloses a method and a system for detecting direct current circuit failure. The method comprise the following steps of inversing a high-capacity accumulator into high frequency alternating current via IGBT, and rectifying the high frequency alternating current to obtain discharge direct current; loading the loading the discharge direct current on a to-be-detected circuit; determining present current and voltage of the to-be-detected circuit, and calculating the resistance of the to-be-detected circuit based on the present current and the circuit voltage; and analyzing the resistance of the to-be-detected circuit based on a preset circuit abnormality determination standard, and determining whether the to-be-detected circuit is failed. A heavy current having an external power supply is adopted to excite the to-be-detected circuit in the invention, so that the failure point concealed in the to-be-detected circuit is exposed, and subsequently the to-be-detected circuit is tested. Moreover, the detection accuracy is improved by the four-wire system measuring technique and the current reversed technique.