A method and a system for fusing images in an image processing field are described. The method includes: capturing at least two frames of images having different intensity under different exposure time in the same scene; fusing the images having different intensity values according to an intensity mapping relation between every two frames of images in the images having different intensity values, and obtaining a fused image is, in which the intensity mapping relation represents a corresponding relation between an intensity value of a pixel location in a bright image and that at the corresponding location in a dark image. Through the method and the system for fusing the images according to the present invention, the dynamic range of the image is enhanced, and the fusing process has a desired result and is easy to implement.