Abstract: According to the character of primary QI impurities composed of carbonaceous particles with the size of several micrometers, the coal tar was purified by the solvent flocculation method. Using the purified tar as raw material, high performance impregnating pitch with low QI content was prepared. The rheologic behavior and permeability of high performance impregnating pitch were comparatively studied. It has been confirmed that the high performance impregnating pitch modifies greatly impregnation efficiency. The mechanical characteristics of C/C composite have been evidently improved.