Abstract: The relationship between the flexural strength,fracture toughness and TiC particle sizein TiC_P/SiC composite was investigated.The effects of cool treatmemt on the properties of TiCY/SiC composite were studied.The results obtained show that the addition of TiC particle can enhance the strength and toughness of the composite,but there is only a very narrow particle size range of enhancing strength and toughness simultaneously.Cool treatment not only increases further the toughness and strength but also changes the toughening extent of TiC particle size,making wider the overlapped particle size extent of strengthening and toughening.Thereby,a strengthening and toughening region is formed.It provides the basis for designing the strengthening and toughening of materials and for formulating the corresnonding technological process.