The wedge support robot is the core module of the intelligent dismantling equipment for the bolster spring and wedge of railroad wagon. In this paper, to address the problem of accurate positioning of bolster hole with abnormal geometry and large error in the complex background, a light-weight object detection model is proposed based on GhostNet and model pruning algorithm: Pruned-Ghost-YOLOv3. The proposed models and the original YOLOv3 model are trained and evaluated on the bolster hole custom dataset. The results show that the improved Pruned- Ghost-YOLOv3 model is smaller, has fewer parameters and is faster compared to the original YOLOv3 model. To meet the requirements of operational efficiency and reliability, a precise positioning algorithm based on the bounding box of the bolster hole and an indirect positioning process are proposed in this paper. The comparative experiments of bolster hole positioning and wedge support are conducted on the wedge support robot. The experimental results show that the proposed Pruned-Ghost-YOLOv3 model can meet the requirements of rapid detection and positioning of the bolster holes, and the proposed precise positioning algorithm and robot positioning process have high accuracy and reliability. The research results are successfully applied to the development of a railroad wagon wedge support robot, and it has a good reference value for the development of the intelligent positioning system of heterogeneous workpiece operation robots in the complex background of related industries.