Abstract: The FDK algorithm is a classic cone-beam approximate reconstruction algorithm,which has been widely used in practice.Ideal imaging geometry is a basic condition in the application of the FDK algorithm.However,it is difficult to satisfy this condition in a practical cone-beam CT system.Reconstructed images will suffer from artifacts caused by the misaligned geometry of the CT system.Therefore,calibration of the CT system in advance is an important and necessary task.Misaligned parameters of the CT system will be taken into the reconstruction algorithm after calibration to improve image qualities in the case of the misaligned CT system.Key points on application of the proposed calibration method for cone-beam CT are discussed deeply in this paper.And calibration result and reconstructed results of an X-ray cone-beam CT are given which prove the validity of the proposed calibration method.