State equation method for calculation of seepage-stress coupling field is developed. First the Biot equation is meshed by finite element method in the spatial domain; and the state equation is used to describe the control equation in terms of a plane strain problem. Then the iterative formula for calculating the displacement at the node is deduced by using the fine integral method. Example shows that the results are good in harmony with the exact results; and that the method could save lots of time as compared with the traditional method.