Abstract: To solve the problem of tiny-size objects and dense occlusion in the transmission line multi-fitting detection task and make full use of the information of fitting high-resolution aerial images, a coarse-fine transmission line multi-fitting detection method based on prior knowledge auxiliary clustering is proposed. First, the coarse detection module is utilized to realize the preliminary perception of the high-resolution aerial images of transmission lines. Then, the determination of clustering algorithm's radius in structural scene sub-region selection module is guided through the prior knowledge for adaptively clustering the appropriate sub-regions. Finally, a fine detection module is designed to fully utilize key information from high-resolution aerial images for precise perception of fittings, and to realize the recognition of fittings from coarse to a finer level by fusing the coarse detection results. The experimental results show that the accuracy of the coarse-fine transmission line multi-fitting detection method based on prior knowledge auxiliary clustering is 11.3% higher than that of the baseline model. Especially, the detection accuracy of tiny-size fittings and dense occlusion fittings is improved obviously.