The invention provides a drop-weight tear test sample fracture shearing area detection method. After a DWTT sample is shorn, a DWTT sample fracture is shot and imaged through a camera, the area of net sections and the area of brittle fracture regions are calculated through image analysis software, and therefore fracture shearing area percentage is worked out. The method is simple and easy to carry out, none equipment needs purchasing, funding is not needed, the brittle fraction regions, especially small brittle fraction regions facilitating brittle fraction region boundary recognition can be freely amplified in the image analysis software, and therefore accuracy of the area of the brittle fraction regions is guaranteed. Due to the adoption of the method that the thickness of the root portion of a sample image notch is measured in the interface of the image analysis software to determine the amplification factor, accuracy of the area of the net sections can be guaranteed, irregular shear lips are prevented from appearing on the hammered side of the sample after sample shearing, calculation accuracy of the area of the net sections is guaranteed, and accordingly scientific and reliable detection data bases are provided for pipeline steel pipe control and fraction prediction.