The cone angle effect of CBCT system and affecting reconstructing slice are discussed. The CC-FDK algorithm is introduced. The redundancy data is not disposed accurately in FDK algorithm. The thesis puts forward a weighting projection method based on cone angle and distance to center plane. The method compensates the information of projection unused in FDK algorithm. The simulation model is scanned and reconstructed. The result indicates that this method can extend the cone angle of scanning.