A B4C ceramic doped with 0.2 at% Si is prepared via hot pressing. The composition and microstructure of the ceramic are characterized by means of X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The electrical conductivity and Seebeck coefficient of the ceramic samples are measured from room temperature up to 1500 K. The electrical conductivity increases with temperature; the Seebeck coefficient also increases with temperature and rises to a value of about 320μV K-1 at 1500K. The value of the figure of merit of 0.2 at% Si-doped B4C is higher than that of undoped B4C and rises to about 1×10-4K-1 at 1500K. The reason for enhancement in the figure of merit of Si-doped B4C is discussed.