AbstractThe calculations of unsteady flow to a multiple well system with the application of boundary element method (BEM) are discussed. The mathematical model of unsteady well flow is a boundary value problem of parabolic differential equation. It is changed into an elliptic one by Laplace transform to eliminate time variable. The image function of water headHcan be solved by BEM. We derived the boundary integral equation of the transformed variableHand the discretization form of it, so that there is no need to discretize the boundaries of well walls and it becomes easier to solve the groundwater headHby numerical inversion.