Abstract: the coal mine wastewater with high salinity is difficult for efficient treatment by traditional coagulation and precipitation methods. we designed an effective process of micro-bubble air flotation system for coal mine wastewater treatmen. The influences of dissolved gas pressure and gas-water ratio on particle size distribution and stability of micro-bubbles were studied, as well as the influences of dissolved gas pressure, gas-water ratio, water salt content, oil content and chemical dosage on oil removal effect were also studied. The results showed that when the microbubble generator is operated under the conditions of 0.55 MPa dissolved gas pressure and 6% gas-water ratio, the stability of the microbubble is the best, the average particle size is as low as 9.24 μm, and the oil removal rate can reach 45.80%. Under the condition of higher oil concentration and higher salt content, the system still maintains 40% treatment effect. Response surface method was used to optimize the dosing combination, and the optimal dosing ratio of PAC dosing concentration of 107.900 mg/L, cationic PAM dosing amount of 10.034 mg/L, and compound demulsifier dosage of 90.000 mg/L was determined. At this time, the removal efficiency of emulsified oil could be increased to 94.52%. Therefore, the micro-bubble air flotation technology has high efficiency and applicability in the treatment of mine water with high salt and high emulsified oil content.