The effect of low-level oxidation (weight loss less than 6wt.%) on mechanical property of two-dimension (2D) carbon/carbon (C/C) composites was investigated in present work. C/C samples were oxidized in a mixture gas, composed of 10vol%O2 and 90vol%N2, at temperatures of 850°C and 1300°C, respectively. The strength of C/C composites before and after oxidation was measured by three point flexural tests. At different temperature, similar influences of low-level oxidation on mechanical property of C/C samples were observed. As a result, failure of the as-received composites was accompanied by brittle, catastrophic reduction in force. As oxidation progressed, the fracture model of oxidized samples changed from brittle model to pseudoplastic failure model. Especially, the changes of flexural strength with the weight loss increasing could be divided into two stages: (i) at low weight loss, the strength increased with weight loss and is slightly higher than that of the unoxidized composites; (ii) at high weight loss, the strength decreased gradually with the weight loss.