The invention discloses an outgoing line detection method for a DC cabinet of a power plant, and relates to the technical field of power systems. The method comprises the following measurement detection steps: detecting the operation state of each line of power transmission lines of the DC cabinet of the power plant, and recording a detection result; extracting all no-load lines according to the recorded detection result; numbering the lines, and sequentially installing voltage detection devices at load ends; collecting the changes of the data measured by the voltage detection devices before and after the switching through the switching of a circuit breaker of a no-load line at a cabinet bus, finding the corresponding line, and carrying out the recording of a line sequence. The method improves the detection flexibility of the outgoing lines of the DC cabinet of a power plant for a worker, irons out the defects of a conventional outgoing line detection method of the DC cabinet of the power plant, reduces the outgoing line detection cost of the DC cabinet of the power plant, and is higher in practicality.