Aiming at the problems of various shapes of foreign matter, high complexity of surrounding environment and low accuracy of existing algorithm in the detection of suspended foreign objects in substations, this paper proposes an improved Faster-RCNN object detection method. Combining Faster-RCNN with feature pyramid networks and deformable convolutional networks, an improved Faster-RCNN object detection method is formed. The detection method strengthens the ability of Faster-RCNN to read semantic information of different scales in the input images, therefore improving its ability on detecting small objects. The image data is used in the image recognition model competition for typical defects of substation equipment, and the simulation experiment is carried out and compared with original Faster-RCNN. The experimental results verify the effectiveness of the proposed method. The improved algorithm, which has higher recognition accuracy and performs well on real detection samples, which can be effectively used in the substation inspection robot system.