In view of the problem that both infrared (IR) image and passive millimeter wave (PMMW) image have limitations in military target detection, a Laplacian pyramid transform-based fusion method was presented in this paper. First, s fusion method based on Laplacian pyramid decomposition was proposed; then, the top decomposed image of IR image was used as the top image of the fusion result and other images were fused by selecting their pixel with maximum absolute value on infrared and passive millimeter wave image corresponding to the layer. After that, the fusion image was obtained by taking the inverse Laplacian pyramid transform. The experiment indicates that the method can effectively fuse important information from IR and PMMW images. The fusion result can better distinguish military targets from the features, it helps to improve the identification ability of composite seeker and keeps it for all-weather operation.