The phenolic carbon matrix precursor was modified by adding pitch and graphite powders. The carbon yield measured both from thermogravimetric analysis and normal carbonization process increased as the powder content increased. The carbon yield from the normal carbonization process has resulted higher value due to the slower heating rate. The bulk densities of c/c composites made from different matrix systems were in the range of 1.35~1.41 g/㎤. From 3-point bending test, the effect of matrix modification was confirmed with the changes in the mechanical properties of the greenbody. As the powder content increases, the mechanical properties of greenbody deteriorated. However, after carbonization the mechanical properties of the c/c composites made from the modified resin with pitch and graphite powder showed higher value than those of the c/c composites made with non-modified phenolic matrix precursor.