A portable three-dimensional digital radiography system, comprising: an X-ray generator; a stand placed on a horizontal plane; a flat panel detector provided on the stand; and a support mechanism comprising: a support tube; a transmission component for driving the X-ray generator to move towards or away from the support tube; a drive component for driving the X-ray generator to rotate; and a support pole slidingly provided in the support tube, and wherein the X-ray generator is detachably provided on the support pole; characterised in that the transmission component comprises: a transmission motor provided in the support pole; a transmission gear; and a transmission rack provided on an inner wall of support tube, and wherein the transmission motor is connected with the transmission gear, the transmission rack is provided in a length direction of the support tube, the transmission gear is engaged with the transmission rack to drive the support pole to slide in the support tube, one end of the support pole far from the support tube is connected with a mounting platform for mounting the X-ray generator, and the mounting platform is detachably connected with the support tube; and the support tube comprises a first support tube and a second support tube, the first support pole is slidingly provided in the second support tube, the support pole is a telescopic pole and is slidingly provided in the first support tube, the transmission rack comprises a first rack provided on an inner wall of the first support tube and a second rack provided on an inner wall of the second support tube, and the first rack and the second rack are spliced with each other. an X-ray generator; a stand placed on a horizontal plane; a flat panel detector provided on the stand; and a support mechanism comprising: a support tube; a transmission component for driving the X-ray generator to move towards or away from the support tube; a drive component for driving the X-ray generator to rotate; and a support pole slidingly provided in the support tube, and a drive component for driving the X-ray generator to rotate; and a support pole slidingly provided in the support tube, and wherein the X-ray generator is detachably provided on the support pole; characterised in that the transmission component comprises: a transmission motor provided in the support pole; a transmission gear; and a transmission rack provided on an inner wall of support tube, and wherein the transmission motor is connected with the transmission gear, the transmission rack is provided in a length direction of the support tube, the transmission gear is engaged with the transmission rack to drive the support pole to slide in the support tube, one end of the support pole far from the support tube is connected with a mounting platform for mounting the X-ray generator, and the mounting platform is detachably connected with the support tube; and the support tube comprises a first support tube and a second support tube, the first support pole is slidingly provided in the second support tube, the support pole is a telescopic pole and is slidingly provided in the first support tube, the transmission rack comprises a first rack provided on an inner wall of the first support tube and a second rack provided on an inner wall of the second support tube, and the first rack and the second rack are spliced with each other. a transmission motor provided in the support pole; a transmission gear; and a transmission rack provided on an inner wall of support tube, and wherein the transmission motor is connected with the transmission gear, the transmission rack is provided in a length direction of the support tube, the transmission gear is engaged with the transmission rack to drive the support pole to slide in the support tube, one end of the support pole far from the support tube is connected with a mounting platform for mounting the X-ray generator, and the mounting platform is detachably connected with the support tube; and the support tube comprises a first support tube and a second support tube, the first support pole is slidingly provided in the second support tube, the support pole is a telescopic pole and is slidingly provided in the first support tube, the transmission rack comprises a first rack provided on an inner wall of the first support tube and a second rack provided on an inner wall of the second support tube, and the first rack and the second rack are spliced with each other.