Computed tomography (CT) is one of the important technical means in the field of security inspection. It is of great theoretical and practical value to study new CT imaging methods for security inspection. In this paper, a triple-source swinging spiral CT (TS-SCT) imaging method is proposed, which can be used for the safety inspection of passenger luggage and express parcels. Three groups of X-ray source-detector uniformly distributed in the circumference are used to swing around the rotation center in the range of 120°, the detected object moves along the axial direction in the scanning field of view, and the swing spiral scanning is realized. Compared with spiral CT, the proposed method does not need the whole rotation, and can use the rotating parts which are easier to manufacture, maintain, and are more wear-resistant than the slip-ring. Moreover, the cable is used to transmit data and power, breaking the limitation of a slip-ring on data and power transmission capacity. The imaging model of TS-SCT is established, the effects of scanning mode, scanning parameters, and ratio r between pitch h and projection height T of a cone-beam near the source in z-direction on imaging efficiency and results are analyzed, and the FDK reconstruction algorithm for TS-SCT is derived. The simulated and experimental results show that the TS-SCT FDK reconstruction algorithm is correct and effective, and the TS-SCT method can be used to realize the 3D imaging of detected objects. On the premise of ensuring imaging quality, r≤1/2 is suggested.