The invention discloses an infrared image enhancement method based on transmission image fusion. The method comprises: carrying out under-segmentation and super-segmentation on an image under different scales through a clustering algorithm, and generating two clustering segmentation results; for the clustering segmentation result, generating two transmission images by using image pure pixel priori; constructing a fusion weight map for each transmission map, constructing an image pyramid structure model for each transmission map and the fusion weight map thereof, and performing layer-by-layer fusion to obtain a fused transmission map; based on the variational model, carrying out edge-preserving smoothing processing on the fused transmission map to obtain an optimized transmission map; and obtaining an enhanced infrared image by using the optimized transmission image. According to the method, a large number of originally hidden scene details in the infrared image can be recovered, and negative effects cannot be introduced.