In this paper, the technology of semi-solid casting was to used are produced Sn-Bi alloy. The influence of agitating time at 125 °C on the microstructure and mechanical properties of of Sn-58Bi casting alloy were discussed. The eutectic Sn-Bi alloy was mechanically agitated during the casting solidification process. The results indicated that non-lamellar Sn-Bi structure with long plate shape, short strip, small size block and suborbicular block shape Sn phase was obtained for different stirring time. The elongation of Sn-Bi alloy with non-lamellar eutectic structure is improved prominently. Compared with the elongation of lamellar eutectic Sn-Bi alloy prepared by conventional die casting, the elongation of semi-solid Sn-Bi alloy with suborbicular block shape Sn phase is enhanced up to 45%.