Abstract: As a high performance thermal-resistant composite, carbon/carbon composites have the highest mechanical strength in the temperature above 1600℃, and the research of C/C gradient materials will extend the application of C/C as a kind of heat insulation in high temperature. To get some information concerning applying density gradient materials, thermal conductivities (with different densities and under various temperatures) were measured. In order to provide a theory in the application of density gradient carbon/carbon composites(C/C), the relationship between these thermal conductivity and density/temperature was summarized; the mechanical properties of 2DC/C and density gradient C/C were investigated. In conclusion, the relationship between the thermal conductivity and density approximately accords with linearity in the experimental range. Density gradient C/C has higher flexural strength and lower thermal conductivity than uniform C/C, which infers that the materials have superiority in heat insulation and structural application.