Mechanical properties of the carbon material utilizing the natural structure of rice bran are investigated. The defatted rice bran is firstly mixed with a phenol resin, and then burned under nitrogen atmosphere to obtain porous carbon particles. In this study, the carbon particles are mixed with the synthesis polymer to get the composite materials. Especially, nylon and polyacetal, which are usually used for gear and so on, are investigated. The effects of particle diameter and weight percent of compounded particles on the tensile properties, fracture toughness and hygroscopic expansion were studied.