The coagulation-flocculation process of new inorganic polymer coagulant, Poly-Aluminum-Silicate-Chloride (PASiC) in the treatment of pulp and paper mill wastewater has been studied. The experiments were carried out in jar tests with PAlSiC dosages range of 10-45 mg/L, pH range of 5-9, rapid mixing at 200 rpm for 2 min, followed by slow mixing at 40 rpm for 15 min and settling for 30 min. The effectiveness of PASiC was measured based on the reduction of turbidity and Chemical Oxygen Demand (COD). PASiC is found to give the highest efficiency in the treatment of the pulp and paper mill wastewater among the other coagulants. It can achieve greater than 90% of turbidity and COD reduction at an optimum dosage of 40 mg/L and pH of 7. A comparison of PASiC performance with that of alum and poly aluminum chloride (PAC) showed that the coagulation efficiency of PASiC is more effective than alum and PAC. The optimum dosages of PASiC, PAC and alum in the removal of turbidity and COD reduction are 45, 150 and 200 mg/L with 93.13, 82.86 and 80.64% for turbidity removal and 91.12, 80.43 and 75.64% for COD reduction respectively. This result suggests that single-polymer system can be used alone in the coagulation-flocculation process due to the efficiency of the PASiC.