The current overhead work robot for transmission line faces issues related to its compact structure and high target localization requirements. To address these challenges, this paper proposes a lightweight bolt detection algorithm based on improved YOLOv8 (You Only Look Once v8) model. Firstly, the C2f module in the feature extraction network is integrated with the Self-Calibrated Convolution (SCConv) module, and the model is streamlined by reducing spatial and channel redundancies of the network through the SRU and CUR mechanisms in the module. Secondly, the P2 Small Object Detection Layer is introduced into the neck structure and the BiFPN network structure is incorporated to enhance the bidirectional connection paths, thereby promoting the upward and downward propagation of features. It improves the accuracy of the network for bolt-small target detection. The experimental results show that, compared to the original YOLOv8 model, the proposed algorithm demonstrates superior performance on a self-collected dataset. In this paper, the mAP accuracy is improved by 9.9%, while the number of model parameters and the model size is reduced by 0.973×10⁶ and 1.7MB, respectively. The improved algorithm improves the accuracy of the bolt detection while reducing the computation complexity to achieve more lightweight model.