Abstract: To investigate the law of bioleaching process of ion−adsorbed rare earth ores, and to guide the development of efficient solvent and optimization of leaching process. The leaching characteristics of ion−adsorbed rare earth ores in Aspergillus niger fermentation system were analyzed by shaking bottle experiment, contact angle measurement, open circuit voltage, Tafel, and electrochemical impedance test. The results showed that the leaching rate of rare earths was more affected by the volume percentage of fermentation liquor and time compared with the temperature, and increased with the increase volume percentage of fermentation liquor and time. The leaching rates of La, Ce, and Y reached 95.84%, 94.44%, and 96.73%, respectively, when the volume percentage of fermentation liquor was 75%, the temperature was 25 ℃, and the time was 30 min. The aluminum silicate minerals in the ore showed weak dissolution. The contact angle between the ore and the solution decreased with increasing volume percentage of fermentation liquor and kept decreasing with increasing time. When the droplets spread out for five seconds, the contact angle was minimum 12.53° in pure water, and 16.38°, 33.52°, 43.78°, and 46.58° in 25%, 50%, 75%, and pure fermentation liquor, respectively. With the increase volume percentage of fermentation liquor, the open circuit voltage and corrosion voltage increase sequentially, and the difficulty of clay mineral dissolution decreases sequentially. The bioleaching of ion−adsorbed rare earth ores was subject to the triple resistance of diffusion of solutes in solution, electron transfer from the interfacial double electron layer, and interfacial by−products.