In this paper, an improved fusion algorithm for infrared and visible images using multi-scale analysis was proposed. First of all, Morphology--Hat transform was used for an infrared image and a visible image separately. Then the two images were decomposed into high-frequency and low-frequency images by contourlet transform. The image fusion method of high-frequency images is based on mean gradient and the image fusion method of low-frequency images is based on PCA (Principal Component Analysis). The experiments and results demonstrate that the proposed method can significantly improve image fusion performance, accomplish notable target information and high contrast and preserve rich details information at the same time.