Fly ash was used as loading material to treat coal mine water containing suspended solids by loading flocculation. Based on single factor test, response surface method was used to optimize the treatment process. A prediction function taking the removal rate of turbidity as response value was established. The optimum reaction conditions of fly ash loading flocculation were determined. The results showed that when the dosage of fly ash was 2.0 g/L, flocculant PAC was 22.8 mg/L and coagulant aid PAM was 0.5 mg/L, the pH of mine water was 7.20 and the turbidity of supernatant was reduced to 2.7 NTU. The removal rate of turbidity reached 99.27%, which was close to the predicted value of 99.45%. The validation test was consistent with the theoretical model, and the regression model was accurate and reliable. Compared with traditional flocculation, the reagent dosage of fly ash loading flocculation was less and the removal rate was higher. The addition of fly ash could adjust the pH value of mine water and promote the flocculation process. Moreover,the leaching rate of trace elements in fly ash was low and would not cause secondary pollution to water.