The effect of ZrO2-3% Y2O3 addition on densification, sintering behavior and mechanical properties of a boron carbide matrix was investigated. When adding 0-30 wt% of ZrO2-3% Y2O3 to B4C sintered densities were increased from 75% to 98.5%. Sinterability was significantly improved by addition of a small amount of ZrO2-3% Y2O3. As a result of density improvement, mechanical properties such as hardness, strength and fracture toughness were increased remarkably. However, when the amount of ZrO2-3% Y2O3 exceed from 20 wt%. Hardness started to reduce.