The original iterative method of the saturated-unsaturated unsteady seepage FEM analysis is presented. According to the character of the iterative process, an iterative coefficient is introduced, and a new method is formed. The improved iterative method can enhance and accelerate convergence of the computation efficiently by selecting suitable , and make the saturated-unsaturated unsteady seepage FEM analysis have broader engineering applicability. Three-dimensional FEM analysis program for saturated-unsaturated unsteady seepage is compiled based on the improved algorithm. The algorithm is validated by an analysis example.