Calculations were performed on the band edge levels of(111)-biaxially strained Si on relaxed Si_(1-x)Ge_x alloy using the k·p perturbation method coupled with deformation potential theory.The results show that the conduction band(CB) edge is characterized by six identicalvalleys,that the valence band(VB) edge degeneracies are partially lifted, and that both the CB and VB edge levels move up in electron energy as the Ge fraction(x) increases.In addition,the dependence of the indirect bandgap and the VB edge splitting energy on x was obtained.Quantitative data from the results supply valuable references for Si-based strained device design. Calculations were performed on the band edge levels of (111) -biaxially strained Si on relaxed Si_ (1-x) Ge_x alloy using the k p perturbation method coupled with deformation potential theory. The results show that the conduction band (CB) edge is characterized by six identical valleys, that the valence band (VB) edge degeneracies are partially lifted, and that both both CB and VB edge levels move up in electron energy as the Ge fraction (x) increases. In addition, the dependence of the indirect of bandgap and the VB edge splitting energy on x was obtained. Quantitative data from the results supply valuable valuable for Si-based strained device design.