Abstract: The minimally invasive thermal ablation technology is different from the traditional surgical operation, which requires the aid of auxiliary equipment to evaluate the ablation results. However, the ultrasound and CT currently used in clinic have shortcomings such as artifacts and radiation. Therefore, this paper proposes and designs a minimally invasive thermal ablation evaluation system based on the principle of electrical impedance imaging to monitor the ablation range. At the same time, the innovative introduction of progra mmable amplified feedforward signal as the parameter signal of the multiplier demodulator in the design of electrical impedance imaging system can effectively solve the problem of weak signal submerged in noise and improve the imaging accuracy. The system controls the excitation size of current signal and the acquisition and processing of boundary voltage through STM32, uploads the collected data to the upper computer, and reconstructs the conductivity distribution through Newton Raphson algorithm, so as to map the ablation area size. The experimental results show that the system can effectively reflect the size of microwave ablation area. Under the same minimally invasive ablation parameters, the average imaging long diameter error is 0.6 mm, the short diameter error is 0.8 mm, and the axial ratio (long diameter / short diameter) error is 1.75%, which has high consistency, verifying the technical prospect of electrical impedance imaging in minimally invasive thermal ablation.