Abstract: SiC/ZrB₂ composites reinforced by SiC nanowhiskers (SiC_W ) and SiC particles (SiC_P) were prepared by a hot-pressing process at 1950℃ under 20 MPa in a flow argon atmosphere. The effects of SiC_W and SiC_P on microstructures，mechanical properties of SiC/ZrB₂ composites were investigated. The results showed that the fracture toughnesses of SiC/ZrB₂ composites with 15 vol% of SiC Wand with 15 vol% of  SiC_P were 8.08 MPa· m^1/2 and 8.515 MPa·m^1/2，respectively. The fracture toughness of the SiC/ZrB-composites with both 15 vol% of SiC_W and 15 vol% of SiC_P reached 9.03 MPa·m^1/2. SiC_W and SiC_P effectively improved the densification of SiC/ZrB₂ composites,and limited the coarsening of ZrB₂ grains，which was in favor of improving the bending strength and fracture toughness of the SiC/ZrB₂ composites. Furthermore，the synergistic effect of SiC_W and SiC_P favored the increase of the toughness.