Difficult for low turbidity water treatment, the treated not reached the drinking water quality standards, the beaker coagulation has been set. In this experiment, the removal effects of low-temperature and low-turbidity water were investigated by using polyaluminum chloride (PAC) and modified active silicic acid. The results indicated that individual addition PAC turbidity removal rate was less than 80%. While adding 67 mg /L PAC and stirring 9-13min, then adding 20 ml /L modified active silica acid of 5% sodium silicate solution and 0.1% polyacrylamide solution with volume ratio of 15:1 and standing 5 min, the coagulant effect was the best and the turbidity removal rate was more than 90%. The optimizing keep time for modified active silica acid was 24 h.