Powder injection molding was adopted to prepare B4C matrix composites with the additions of silicon carbide and zirconia. The B4C nozzles with micro holes were well replicated from the mold, then successfully debound and sintered. The sintering characteristics, microstructures and mechanical properties of the B4C matrix composites materials were investigated. The results show that the additions of SiC and ZrO2 and increase of sintering temperature are in favor of the densification of the B4C matrix composites materials. In addition, the X-ray analysis shows that the sintered composites are composed of B4C. SiC and ZrB2 phases. The morphologies of ZrB2 and SiC phases change from nearly equiaxed to plate-like grains with increasing the sintering temperature. The fracture strength and hardness value of composites sintered at 2240 degrees C reach to 305.9 MPa and 3201 HV, respectively. The sintering model between the linear shrinkage and relative density was also established, predicting the sintering density and revising the measured density by the Archimedes and other methods. The calculated and measured results correspond well with each other. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.