Abstract: B4C-zircaloy was prepared using Zr-2 hydride powder and B4C powder as raw materials, molded by rubber isostatic pressing, sintered in vacuum furnace. The relative density and open porosity were tested by immersion method. The microstructure was analyzed by scanning electron microscope (SEM). Influence of B4C content, forming pressure, sintering temperature, sintering time and sintering aide content on relative density and open porosity of the B4C-zircaloy were investigated. The results show that B4C hindered the densification of sintered body. With increase of B4C content, the relative density of the sintered body decreased. B4C-zircaloy gained a higher density when the forming pressure, sintering temperature and sintering time increased. Sn powder performed sintering aide well for B4C-zircaloy when the content of Sn was below 0.5wt%, otherwise the relative density of B4C- zircaloy decreased.