This research work was aimed to improve the performance of magnetic induction tomography (MIT) system by designing a high-performance excitation source and the optimal excitation coil. A new type excitation source with adjustable output was designed, and then the power circuit was simulated by the software ICPA. Focused and solenoid coils were designed in accordance with the design principle of coil, then the optimal excitation coil was proved by measuring the magnetic field distribution and the experimentation of phase detection using neuron cell models. At the stated excitation frequency, the parameters of the excitation source are output power 0.035 W-31.4 W, steady output peak current over 1 A, frequency stability 10(-9), and THD amplitude less than -51dB. When compared with other coils, the focused discal excitation coil is most effective for phase detection with the use of neuron cell models. The excitation source can produce the stated frequency sine wave with higher frequency stability, lower THD and wider adjustable output power. The phase difference between normal cell model and edema cell model was more significant by measurement using focused discal coil.