The production of smoke is a sign of fire occurrence, and in the monitoring and prevention of disasters, the research value of smoke is higher than that of flames. Segmentation of smoke targets is of great significance for the study of smoke characteristics. However, traditional methods for smoke target segmentation are limited in accuracy and are easily affected by the scene. Existing smoke segmentation models rely on a large-scale classification backbone, which sacrifices high-resolution feature mappings to achieve deeper architectures. These models neglect the relatively important local details and global contrast information that are crucial for smoke segmentation, and their segmentation results for smoke edge details are also not satisfactory. In this paper, the Sobel operator and multi-scale convolutional encoder are fused for feature extraction, and the residual mixing attention mechanism as well as the edge segmentation module are added to the model, and a multi-scale segmentation model for fire smoke edge segmentation is proposed, which improves the segmentation accuracy, segmentation precision and edge segmentation. The test results of the homemade smoke segmentation dataset show that the model's mIoU can reach up to 90.48% and finally stabilized at 90.09%, mPA is up to 96.96%, MAE is reduced to 0.02, and MaxF1 reaches 94.37%, which is superior to the current semantic segmentation model. Compared with the base model U2-Net improves 3.26% (AVG20) and 2.68% (TOP1) in mIoU metrics, and 0.95% and 1.36% in mPA and MaxF1 metrics, respectively. The method proposed in this paper is more suitable for fire smoke segmentation, which is important for smoke characterization and smoke source point identification research.