Abstract: This paper investigated the effects of pressureless sintering in suit synthesis process on the density, physical properties and microstructure of ZrB₂/B₄C ceramic composites. The results showed that, as the sintering temperature increasing and the holding time extending, the density increased first and then decreased, and the maximum relative density of the composites synthesized at 2 060℃for 30 min was 93.2%; the hardness rised with increasing temperature and its value reached to the peak at 2 070℃; opposite to the hardness, the fracture toughness decreased from 4.04 MPa·m^1/2 at 2 000℃ to 2.36 MPa·m^1/2 at 2 060℃.