Abstract: Based on the assumptions of surrounding rock submitting to the behavior of three-element visco-elastic model and the initial earth stress field being linear, a method for three-dimensional back analysis of initial earth stresses, elastic constants E1, E2, v and viscous parameter η2 is established. The BEM is employed. Boundary convergence displacement values, internal relative displacement and disturbed stress values measured in situ are basic informations for back analysis. By using interpolation function, boundary planes could be divided into elements freely without considering places of measuring points along the boundary. Finally, a test example and a practical case study are given to verify the methed.