Novel microwave synthesis cationic hemicelluloses from sugarcane bagasse were obtained by quaternization with CHMAC using sodium hydroxide as a catalyst in microwave synthesis condition. The parameters including the dosage of hemicellulose/CHMAC, the microwave time and the microwave power were optimized and the extent of quaternization was measured by zeta potential. As paper additive, the effect of cationic hemicellulose on bleached bagasse was researched. Then pulp handsheet properties were studied. The results indicated that adding the cationic hemicellulose could increase paper mechanical strengths, and its effect was better than original bleached bagasse pulp. At the dosage of 0.8% on oven dried pulp, paper tensile index, tensile strength, breaking length, burst index and folding endurance can be increased by 43.79%, 36.95%, 33.11%, 17.35%, 33.33% respectively, much better than the paper without the cationic hemicellulose.