Lung diseases, such as pleural effusion, may seriously affect the life quality of the patients. Clinically, the lung auscultation method and some lung imaging approaches, such as chest X-ray, computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI), are frequently used to evaluate the state of pleural effusion. However, most of the above imaging approaches may encounter the radiation issue and require the experienced operator and the relative expensive cost. The technique of electrical impedance tomography (EIT) is a novel imaging approach providing the rapid, noninvasive, and radiation-free measurement. Based on the EIT technique, a novel wireless EIT system was proposed for pleural effusion analysis in this study. Different from other EIT systems requiring many electrode leads and disposable Ag/AgCl electrodes, conductive foam-based dry electrodes and the specific belt mechanism design were designed to improve the convenience of use and provide a good stretchability to fit different body sizes so that it can be suitable to get better human signals and long-term use. Moreover, several indexes related to pleural effusion were also defined from the change of the EIT image of the lungs during the breathing activity. Finally, the phantom and human experiments were tested to validate the system's performance. The experimental results show the pleural effusion state exactly reflected on the defined indexes extracted from the EIT image.