The Bi_Mn wt6% alloys were solidified from semi_solid state in a magnetic field. The microstructure and magnetic properties have been studied systematically. The results show that the samples were of a eutectic structure of double phases and have large anisotropy. It was shown that the alignment of MnBi crystals occurred along the induced field. With increasing induced magnetic field, the remanence(Mr) increased gradually, which shows that the higher the induced magnetic field, the better the alignment. The spin reorientation temperature (TSR) for MnBi alloys increases with increasing induced magnetic field. The effects of the induced field on the microstructure and the magnetic properties of Bi_Mn wt6% alloys were also discussed.