Abstract: A computational inverse technique is presented for determining the detonator status in an underground explosion from the given damage effects. In this technique, the detonator status can be determined by minimizing the error functions formulated using the given damage effects and those computed using the forward solvers based on the candidates of the detonator statuses. To reduce the computational cost, the polynomial approximation model based on error reduction ratio is used to replace the actual computational model. The nonlinear Newtons method is employed as the inverse procedure. In order to improve the computational efficiency, the trust region method is adopted to manage the error between the approximation model and the actual one. Additionally, the Tikhonov regularization method is applied to the ill-posed problems. The results demonstrate that the detonator status can be determined from the given damage effects with high efficiency through innovative use of the present method.