The effect of humic acid (HA) on the stability of nano-TiO₂ was analyzed, and the effects of coagulant dosage, pH and calcium(Ⅱ) concentration on the removal efficiency of HA-TiO₂ composite pollutants by the coagulation-ultrafiltration process were investigated. The results showed that the electrostatic adsorption and coordination reaction occurred between nano-TiO₂ and HA in the aqueous solution, which caused the decrease of effective particle size of nano-TiO₂, the enhancement of electrostatic repulsion, more uniform dispersion of colloid, the increase of system stability and easy migration. These posed a threat to the safety of drinking water. The optimum parameter for HA-TiO₂ composite pollutants removal was that the coagulant concentration is 0.46 mmol/L, and the initial pH value is between 7 and 8,the higher membrane flux and lighter membrane fouling was achieved under this condition. The calcium ion in the solution will lead to the increase of membrane fouling.