Abstract: For preparation of sulfated polysaccharides isolated from bamboo leaves(Indocalamus tesselatus) with chlorosulfonic acid-pyridine, the experimental conditions as the molar ratio of reactants and temperature and time of reaction were discussed. A homogeneous sulfation method with good yield of more than 80% was obtained and the sufur content was found to be 21.9%. Conformation change in sulfated polysaccharide with changes of intrinsic viscosity, polarimetery and CD spectra were found to be related to the negative charge. The polysaccharide sulfates were shown to have better activity to inhibit cytopathic effect of human immunodeficiency virus(HIV) infection than native polysaccharides.The effectiveconcentration was 10μg·ml^-1 while the cytotoxic concentration was 2.5 mg·ml^-1.