Silicon carbide (SiC) based ceramic composites with improved fracture toughness and increased flexure strength have been developed by incorporating some other non-oxide and oxide particles or some whiskers and fibres. Hot-Isostatic Pressing (HIP) has been identified as an important technology for strengthening carbide by surface modification. In this paper, Hot-pressed SiC-TiC with different densities and HIP-SiC/SiC(w) composites were post HIPped under a N2-pressure of 200MPa at 1850°C for lh. The results showed that the open pores were closed and physical and mechanical properties such as density, flexure strength and toughness were obviously improved. For the SiC-TiC composites, the final density can be reached above 98% theoretical density, flexure strength and fracture toughness were increased by 100% and 30-50%, respectively. For the SiC/5vol%-SiC(w) composites, the final flexure strength and fracture toughness were increased from 595 MPa and 6.7 MPa m1/2 to 920MPa and 8.5 MPa m1/2 separately. A possible reaction-HIP densification mechanism for SiC ceramics with open pores is proposed.