1. A method for correcting a diffusion image having an artifact, the method comprising: (a) providing a set of diffusion images comprising the diffusion image having the artifact; (b) calculating a first signal intensity of each image in the set of diffusion images; (c) plotting a graph of serial number of slice of the set of diffusion images versus the first signal intensity; (d) calculating a second signal intensity of the diffusion image having the artifact by performing interpolation on the graph; and (e) correcting the diffusion image having the artifact base on the second signal intensity.