In order to study the effect of heterogeneity of leaching solution on leaching rate and leaching depth in ionic rare earth ore body, an infiltration test was carried out in the ion-type rare-earth mine in Anyuan of Jiangxi with the mixed solution of brilliant blue and ammonium sulfate, in which brilliant blue was used for tracing the permeation process of leaching solution while ammonium sulfate used for reflecting the permeation process of ion exchange. The inhomogeneous permeation process of the solution in ore body was obtained, and morphological image processing technique was used to determine the parameters of dyeing images and the widths of multi-fractal spectra of the staining profiles. The effect of inhomogeneous permeation process on the leaching depth of rare earth ions was also analyzed. The results showed that the variation coefficient of inhomogeneous parameters were medium, leaching agent had multi-fractal properties in inhomogeneous permeation process. Multi-fractal spectrum width and preferential flow fraction were more sensitive to inhomogeneous permeation process compared with the depth of matrix flow, the dyeing image parameters, such as the dyeing depth and dyeing area ratio. With the increase of the preferential flow fraction, the leaching rate and the leaching depth decreased.