Abstract: The stability of cemented tailing filling body plays a core role in backfill mining as bearing body. In recent years, mineral processing wastewater is reused for filling mining to reduce a series of problems such as environmental pollution in some mines. It is extremely important to find out the impact of mineral processing wastewater which use it to filling on the strength of cemented tailing filling body in the mines. Therefore, cemented tailing filling body specimens (curing ages=7 d, 14 d, 21 d, 28 d) have been prepared with mineral processing wastewater (pH=7, 8, 9) and ordinary tap water (pH=7). The uniaxial compressive strength, microstructure, and the process of failure of acoustic emission (AE) count rate, ib value and energy of cemented tailing filling body were analyzed by using AE, scanning electron microscopy (SEM) and X-ray diffraction (XRD) test. The results show that: ① At the same age of maintenance, the strength of cemented tailing filling body which mixed mineral processing wastewater is lower than that mixed ordinary tap water, the strength decreases with the increase of pH value, and the grey correlation between \rmCO_3^2 - and the uniaxial compressive strength index of the filling body is the best, while the correlation of Ca²⁺ is the worst, and the correlation for anions is better than for cations overall; ② Under the same curing age, the mass concentration and diffraction peak intensity of C—S—H gel in the filling body mixed with mineral processing wastewater are lower than those of the filling body mixed with ordinary tap water, while the mass concentration and diffraction peak intensity of ettringite are higher than those of the filling body mixed with ordinary tap water; With the increase of pH value of mineral processing wastewater, the mass concentration of C—S—H gel in the filling body decreases and the intensity of diffraction peak decreases, while the mass concentration of ettringite increases and the intensity of diffraction peak increases, which leads to the decrease of filling body strength; ③ AE count rate and ib value show the laws of “rise-drop-sudden increase-peak value” and “fluctant rise-sharp drop-gradual rise” during the failure process of the filling body; AE b_i1, b_i2, b_i3, the cumulative counts rate per 10 s and energy value at the peak stress of the filling body which mixed mineral processing wastewater are less than those of mixed ordinary tap water, moreover, the above AE characteristic indexes gradually decrease with the increase of pH value of mineral processing wastewater.