Disclosed are a CT device and a method thereof. The CT device comprises an annular electronic gun array, an acceleration cavity, an annular transmission target and an annular detector, wherein the annular electronic gun array comprises a plurality of electronic guns, and every electronic gun sequentially emits electron beams in the radial direction of the annular electronic gun array according to a predetermined pulse sequence the acceleration cavity is arranged on the annular inner side of the annular electronic gun array, comprises a plurality of concentric coaxial cavities nested together, works in a pi mode and is used for sequentially accelerating the electron beams emitted by every electronic gun of the electronic gun array the annular transmission target is arranged on the annular inner side of the acceleration cavity, is bombarded by the accelerated electron beams and generates X-rays and the annular detector receives the X-rays having penetrated an examined object.
