Polysilanes with antimony side groups (PSA) can be synthesized from polymer reaction of polymethylsilane at room temperature. In so doing, the yield of polymer is 75.2% and the average molecular weights of the polymer are around 1600. Its chemical composition and structure can be characterized by elemental analysis, FT-IR, 1H-NMR,²⁹Si CP/MAS NMR, GPC, and UV. It is soluble in the common organic solvent; the UV absorption maximum wavelength is 330nm. The property of pyrolysis shows that its ceramic yield is 80% and it is a potential preceramic polymer. This polymer shows good semiconductive properties, whose intrinsic conductivities are within the range of 10^-8～10^-7S/cm, and can be increased above 10^-5S/cm after being doped with iodine.