Abstract: Electrical impedance tomography (EIT) is a technique that uses an array of electrodes to deliver safe stimulating currents, and measures the boundary voltages between adjacent electrode pairs in the array in sequence. It then reconstructs the distribution of impedance in all or part of the tissue using reconstruction algorithms, to achieve structural and functional imaging. EIT technology for the lung has the characteristics of continuous, radiation-free, non-invasive, and can be used for real-time dynamic monitoring of the lung in critically ill patients. This paper introduces the basic principles of lung EIT, analyzes the research progress and existing problems of the technology from the perspectives of hardware systems, imaging algorithms, and clinical applications (lung ventilation, lung perfusion, and lung function assessment), and discusses the development direction to provide ideas for expanding the clinical application of lung EIT.