The invention discloses an electric-power line detection method and system based on millimeter wave radar decision tree classification. The electric-power line detection method based on millimeter wave radar decision tree classification includes the steps: utilizing a millimeter wave radar carried on an unmanned plane to acquire a radar image of an electric-power line; transformation of coordinates: utilizing a method of transformation of coordinates to transform the radar image of the electric-power line to a rectangular plane coordinate system from a polar coordinate system; image processing by block: taking the distance in the image as the standard, setting a threshold, and blocking the image according to the set threshold; utilizing Hough transformation to detect the linear segments existing in the image blocks; obtaining a candidate linear segment set; and utilizing a decision tree classification model to classify the linear segments in the candidate linear segment set so as to detect the position of the electric-power line. The electric-power line detection method and system based on millimeter wave radar decision tree classification have the advantages of being able to effectively detect the electric-power line target in real time and being relatively low in the false alarm probability.