neither the complicated and changeable seepage field nor the action of three direction seepage factors at the same time can be fully reflected in the two-dimension model;as a result the real seepage field cannot be acquired.A three-dimension mathematical model is set up;and both section and terrain are simplified.An example is given;and the result is compared with that of the test.The better identical result indicated that the three-dimension model must be adopted in the seepage analysis of the complicated topographical tailings dam;and the appropriate predigestion can satisfy the precision and reduce the complicity and difficulty.