The invention relates to an in-situ leaching method of electric field strengthened fine grain tailings. The method comprises the following steps of: changing a fine grain tailings pond into an in-situ leaching system by embedding electrodes, drilling filling ports and pumping filling ports without destroying the original tailings pond structure, controlling the flowing direction and flowing speed of infiltration liquid through the strengthening function of the electric field to meet a standard of infiltration liquid, and extracting valuable metal in an extraction and electrodeposition plant. Through the strengthening function of the electric field, the flowing speed of the infiltration liquid and the migration speed of solute are accelerated, the problem that the fine grain tailings pile body is poor in permeability and low in leaching efficiency is solved, the fine grain tailings pile body meets the requirement of environmental protection by regulating the pH value of the infiltration liquid, the use ratio of the tailings resources is improved, the environmental influence is avoided, and the safety of the tailings pond is improved by electrifying continuously after leaching for electroosmosis strengthening. The in-situ leaching method is a novel efficient and environment-friendly tailings disposal technique, and has a great significance in alleviating the imbalance between the supply and demand of mineral resources in China.