The application of active fillers, Al, Cr, TiH₂ and Zr, in the preparation of polycarbosilane (PCS) derived ceramics was investigated. The results showed that the inclusion of active fillers could decrease the porosity of the green compacts effectively, increase ceramic yields of PCS by reacting with N₂, free carbon and/or gas volatile of PCS during pyrolysis to produce new compounds. It was found that Al and Cr could restrain the linear shrinkage of the green compact upon pyrolysis. While TiH₂ and Zr could not. The linear shrinkage got higher with increase of the volume ratio of TiH₂/PCS and Zr/PCS. It was also shown that the inclusion of Al and Zr could enhance the three-point bending strength of the resulted ceramics with the strength of 212MPa and 104MPa when the volume ratio of Al/PCS and Zr/PCS were 60% vol, respectively, which were accordingly 3.3 and 1.6 times of that of the resulted ceramic in which active filler was not included. The inclusion of TiH₂ and Cr, however, could not enhance the strength. So Al was thought as the best among the four fillers. The phase compositions of pyrolysis products were analyzed using X-ray diffraction( XRD). Fracture surfaces of specimens after three-point bending tests were examined on the scanning electron microscope(SEM).