A built-in electrode electrical capacitance tomography sensor, wherein, the electrical capacitance tomography sensor is barrel in shape, which sequentially comprises, from inside to outside, array-distributed electrodes, an electrode insulating sleeve, a flange outer tube, an insulating tube and a signal transmission line; wherein the array-distributed electrodes are N electrode sheets, each of which has the same size and consists of a measuring end and a fixed end, and N is an integer in a range from 8 to 16; wherein the array-distributed electrodes are formed by tile-shaped electrodes with an arc cross section, which are made from high temperature resistant metal conductors through turning and wire cutting processes; wherein an outer arc surface of each tile-shaped electrode is provided with a metal screw stem which is used to fix the electrode; wherein the tile-shaped electrodes are uniformly fixed on an inner wall of the electrode insulating sleeve by positioning of the metal screw stem, the metal screw stem passes through both the electrode insulating sleeve and the flange outer tube, an outer end of the metal screw stem is sleeved with the insulating tube, which makes the metal screw stem insulated from the flange outer tube; wherein the signal transmission line comprises a high temperature section-signal transmission line and a normal temperature section-signal transmission line, both the high temperature section-signal transmission line and the normal temperature section-signal transmission line are a shielding line consisting of a cable core, an insulating layer and a shielding wire mesh, wherein all elements of the electrical capacitance tomography sensor are resistant to a high temperature of 1000 °C; wherein one end of the cable core of the high temperature section-signal transmission line is provided with a metal disc which is fixed on the metal screw stem, the other end of the cable core of the high temperature section-signal transmission line is connected to the cable core of the normal temperature section-signal transmission line, and the shielding wire meshes of the two sections of the signal transmission line are connected separately; wherein the shielding wire mesh of the high temperature section-signal transmission line is connected to the flange outer tube to complete the signal shielding; and wherein the electrodes are connectable to an electrical capacitance tomography signal acquisition system through the signal transmission line, so that the collected capacitance data can be transmitted to the electrical capacitance tomography signal acquisition system via the signal transmission line, and then transmitted to an imaging computer to complete image reconstruction. wherein the array-distributed electrodes are N electrode sheets, each of which has the same size and consists of a measuring end and a fixed end, and N is an integer in a range from 8 to 16; wherein the array-distributed electrodes are formed by tile-shaped electrodes with an arc cross section, which are made from high temperature resistant metal conductors through turning and wire cutting processes; wherein an outer arc surface of each tile-shaped electrode is provided with a metal screw stem which is used to fix the electrode; wherein the tile-shaped electrodes are uniformly fixed on an inner wall of the electrode insulating sleeve by positioning of the metal screw stem, the metal screw stem passes through both the electrode insulating sleeve and the flange outer tube, an outer end of the metal screw stem is sleeved with the insulating tube, which makes the metal screw stem insulated from the flange outer tube; wherein the signal transmission line comprises a high temperature section-signal transmission line and a normal temperature section-signal transmission line, both the high temperature section-signal transmission line and the normal temperature section-signal transmission line are a shielding line consisting of a cable core, an insulating layer and a shielding wire mesh, wherein all elements of the electrical capacitance tomography sensor are resistant to a high temperature of 1000 °C; wherein one end of the cable core of the high temperature section-signal transmission line is provided with a metal disc which is fixed on the metal screw stem, the other end of the cable core of the high temperature section-signal transmission line is connected to the cable core of the normal temperature section-signal transmission line, and the shielding wire meshes of the two sections of the signal transmission line are connected separately; wherein the shielding wire mesh of the high temperature section-signal transmission line is connected to the flange outer tube to complete the signal shielding; and wherein the electrodes are connectable to an electrical capacitance tomography signal acquisition system through the signal transmission line, so that the collected capacitance data can be transmitted to the electrical capacitance tomography signal acquisition system via the signal transmission line, and then transmitted to an imaging computer to complete image reconstruction.