The principle of a true color low light level night vision system based on full-wave and three-wave bands is briefly described. Combining with the general image fusion algorithms, four image fusion algorithms for low-light-level night vision, including the weighted average method, the Brovey method based on linear transformation enhancement, the HIS (hue, intensity and saturation) space method, and the HIS method based on edge segmentation are studied. The realization methods and processes of these fusion algorithms are described in detail. The research results show that by the Brovey method based on linear transformation enhancement, the comprehensive objective evaluation indexes of fusion images for Scene 1 and Scene 2 are 27.9647 and 31.2756, respectively, larger than those by the other three algorithms. Among these four fusion algorithms, the visual effect of fusion images obtained by the Brovey method based on linear transformation enhancement is the best.