B4C ceramics were fabricated by spark plasma sintering (SPS) technique with 5 vol.% silicon as sintering additive. Optimization of SPS method production parameters for B4C ceramics having geometries 50 x 50 x 5 mm, square cross section will be performed. The sintering process was carried out at different temperatures by applying 40 MPa of pressure under vacuum atmosphere. The effect of silicon additive, sintering temperature and different soaking times on density, vickers hardness, fracture toughness and microstructure were examined. The mechanical properties of the B4C ceramics having silicon as additive were compared with the results of monolithic B4C. The hardness and fracture toughness of the samples were evaluated by the vickers indentation technique. Microstructures of spark plasma sintered B4C samples with different parameters in square cross section were characterized by using SEM technique.