[en] Using the first-principles band-structure method and a special quasirandom structure (SQS) approach, we have systematically calculated the alloy bowing coefficients and the nature band offsets of Sn_xZn_1-xTe alloys. We show that the bowing coefficients and band gaps of these alloys are sensitively composition dependent. Due to wave functions full overlapping and delocalization of the Sn outermost p orbits and Zn s orbits, the coupling between these states is very strong, resulting in a significant downshift of conduction band edge with the increase of the Sn concentration x, While the valence band edge keeps almost unchanged compared with that of the binary ZnTe, thus improving the possibility for ambipolar-doping. (condensed matter: electronic structure, electrical, magnetic, and optical properties)