Abstract: In order to realize the vision of building a beautiful，ecological and green mine，and treat the acid water pit in the mine more scientifically，economically and efficiently，research on the re-under⁃ standing and treatment technology of acid water in the reservoir has been carried out at a certain iron mine in Maanshan City cooperation with universities and other institutions. The results showed that: ① The physico⁃ chemical indicators of water in different layers of the acid water pit vary significantly，and the overall trend is a gradual change; The pH value of the water body ranges from 3.33 to 3.69 and increases with the increase of water depth. The dissolved oxygen and oxidation-reduction potential of the surface water are relatively high，while the contents of nutrients such as nitrogen and phosphorus and the concentrations of metal ions are relatively low. There is a small amount of organic matter dissolved in the acid water.② The high-pres⁃ sure seepage and direct discharge of acid water will pollute groundwater and downstream water systems，cor⁃ rode the equipment and flow-through parts it comes into contact with，thereby increasing the frequency of maintenance and inspection and production costs，and endangering the healthy growth of humans，animals and plants. ③ When treating acid water with 10% lime milk，compared with the on-site single-stage neu⁃ tralization treatment process，the staged treatment process is more convenient to operate and manage，has a lower production cost，and can solve the problem of the manganese ion concentration in the effluent from the on-site process not meeting the standard. The precipitate is a non -toxic general Class I industrial solid waste，and there is no secondary pollution problem when it is landfilled in a Class I landfill. ④ The rich and diverse microorganisms in water bodies are one of the key factors in increasing the dissolved oxygen concen⁃ tration in water，accelerating the oxidation of ferrous ions and the hydrolysis and precipitation of trivalent iron，and reducing the pH value of water. They also have the ability to slowly adsorb and precipitate heavy metal ions. Seasonal temperature changes mainly indirectly affect the physical and chemical indicators of wa⁃ ter bodies by influencing the activity of microorganisms. To accelerate the in-situ self-repair ability of acid water pits，it is of great significance to input reasonable exogenous organic matter. Research showed that the staged treatment process combined with in-situ microbial remediation technology is a green，environmental⁃ ly friendly and low-cost process for the treatment of acidic wastewater in mines.

Key words: acid mine wastewater, pyrite, chemical oxidation, biology oxidation, pH value, heavy metal iron, neutralization, sedimentation