A system for electrical impedance tomography and method thereof are disclosed, by which electrical characteristics within a measurement target can be precisely detected. The present invention includes the steps of injection a current to a measurement target via at least one electrode pair selected form a plurality of electrodes (250) attached to the measurement target, detecting voltage of a surface of the measurement target using a plurality of voltmeters (260) connected to the electrodes that are not selected, respectively, adjusting gains of the voltmeters according to maximum values of the detected voltages, respectively, amplifying the detected voltages using the gain-adjusted voltmeters, respectively, and imaging an internal part of the measurement target based on the amplified voltages.