Electrical Capacitance Tomography technology has “soft field” characteristics. Aiming at the problem of low sensitivity in the central area of the sensitive field, an InternalExternal Electrodes based on combination electrodes was designed. Simulation of InternalExternal Electrodes sensor with Different Number of Electrodes has conducted by using Matlab2014a and COMSOL5.3. Based on these software, a twoelectrode rotating excitation measurement method was adopted. Landweber iterative algorithm were used for Image Reconstruction of Circular and Annular Regions in ECT Sensitive Field. The simulation results show that comparing with the traditional ECT capacitance External Electrodes sensors, the InternalExternal Electrodes sensor could improve the sensitivity of the center area in most sensitive fields and improve the accuracy of image reconstruction, and the correlation coefficient gets increased up to 0.92, and it indicates that the InternalExternal Electrodes sensor is feasible and effective in ECT image reconstruction.