ABSTRACT: In this paper, the superposition boundary algorithm is coupled into the Discontinuous Deformation Analysis (DDA) as a nonreflecting boundary condition for wave propagation modeling in infinite media. One-dimensional wave propagation modeling in a jointed rock bar indicates that the absorbing ability of the superposition boundary varies with different values of the stiffness of the constraint spring which is introduced in this nonreflecting boundary algorithm. The absorbing ability of the superposition boundary condition (SBC) is compared with the viscous nonreflecting boundary which was employed in the DDA by some researchers. The absorbing ability of the Viscous Boundary Condition (VBC) varies under different boundary block edge length and stress wave incident angle conditions. Comparatively, through the adjustment of the constraint spring stiffness, the SBC could absorb the reflections satisfactorily under various values of the boundary block edge length and the stress wave incident angle.