Although the underwater tunnel is under a rapid development nowadays, the theoretical research methods, including reflection and angle transformation, are still in their infancy. At present, almost all the studies are based on the hypothesis that soil layers are homogeneous, but most of the soil layers are anisotropic in actual soil engineering. Therefore, an analytical derivation method of flow field in heterogeneous media based on the traditional equiangular transformation method is presented. Numerical simulation shows that with the increase of the anisotropic permeability coefficient ratio, the contour line of approximate ellipse becomes flat. On the contrary, the lateral permeability is proportional to the upgrade of the anisotropic permeability coefficient ratio and the permeability appears the same trend. © 2023 Tianjiao Zhang.