Cationic Starch (CS) and Carboxymethyl Cellulose (CMC) were taken as binary strengthening system of paper. The strengthening degree of the binary strengthening system was studied. The result showed that the tensile index of paper improves 6. 4% when using about 2. 2% on dry weight of the cellulose CS alone; when using 4. 4% CMC alone, the tensile index of paper improves 2. 6%; when the ratio of CS :CMC is 10 :0. 8 and the total adding amount is about 2. 2% on dry weight of the cellulose, the improvement of the paper's tensile index reaches over 15%.