The basic working principle of Cone Beam Computer Tomography (CBCT) is briefly described, the advantages and disadvantages of both continuous and pulsed X-ray imaging methods are analyzed, and the pulsed X-ray imaging method is adopted to implement the design of low-dose CBCT. On the basis of this, the internal and external trigger modes of PaxScan 2520 flat panel detector are realized. The experiment results show that the method of continuous X-ray imaging needs dozens of seconds for the process rotating a circle, in the meanwhile, the method of pulsed X-ray imaging only needs about four seconds for doing same job. In a word, pulsed X-ray imaging reduces the X-ray radiation time considerably and improves the safety performance of CBCT significantly. Besides, pulsed X-ray imaging with internal and external trigger modes has no difference in terms of image quality. The choice for the modes depends on whether or not needs active control for X-ray emission.