Abstract: In response to the issue of small particle size and difficult removal of suspended particles in the mine water of Baorixile open-pit coal mine, this study probed into the optimal parameters of the coagulation and precipitation process through single-factor and orthogonal experiments, and explored the mechanism behind the coagulation of fine particles in mine water.The optimal process parameters for coagulation and precipitation include: 50 mg/L of polyaluminum chloride (PAC), 5.0 mg/L of non-ionic polyacrylamide (NPAM) under 1 minute of rapid stirring (300 r/min), 8 minutes of slow stirring (50 r/min), and 5 minutes of settling.Under these optimum process conditions, the concentration of suspended solids (SS) is 5.0 mg/L with a removal efficiency of 99.1 %.Compared to the sole addition of PAC, the removal efficiency of fine particles below 10 μm increased by 25.9 %.Additionally, theζpotential of the mine water decreased from -40.9 mV to -16.3 mV, indicating that the coagulation mechanism of fine particles is mainly attributed to the adsorption and charge neutralization of PAC and the bridging effect of PAM.