Abstract: The stability of artificial roof in downward cemented cut and fill mining is analyzed by using simply supported beam theory. Cracks will appear when the strength of the filling body exceeds its ultimate strength. Then the artificial roof is in danger of roof falling. Ground penetrating radar (GPR) is an effective means of non-destructive detection. Firstly, characteristics of cracks in single uniform medium are studied by the forward modeling. Secondly, characteristics of cracks in multilateral medium are analyzed, and the two kinds of forward feature are compared. Finally, characteristic of responses of a vertical crack contained in cemented tailings backfill model in the laboratory are studied to find out a group of hyperbolic waves along the vertical direction. The study shows that the cracks in artificial roof of cemented tailings backfill can be detected by GPR and it provides a basis for interpretation in field detection.