Abstract: Bamboo leaf polysaccharide was extracted by phosphotungstic acid coupled with ultrasonic. The extraction process was optimized by single factor experiment combined with response surface experiment. The structural characterization and monosaccharide composition of polysaccharides from bamboo leaves were analyzed by Fourier transform infrared chromatography(FT-IR),scanning electron microscope(SEM)and high performance anion chromatography(HPAEC). And the related biological activities were evaluated. The results showed that the optimum extraction conditions for crude polysaccharides from bamboo leaves were as follows:Ultrasonic temperature 80℃,extraction time 2 h,liquid-solid ratio 1:20 g/mL,phosphotungstic acid mass fraction 4.50%,ultrasonic power 300 W. Under these conditions,the yield of polysaccharide was 9.89%. The bamboo leaves polysaccharides possessed the structure of α-pyranosides and consisted of L-fucose,L-rhamnose,L-arabinose,D-glucose,D-galactose and D-xylose. The polysaccharides from bamboo leaves exhibited antioxidant activities in reducing power,scavenging of DPPH and ABTS free radicals. Moreover,the abilities of antioxidant activity were positively correlated with the concentration of polysaccharides. The inhibitory effect of polysaccharides on the proliferation of cancer cells increased gradually with the concentration increasing of 0.25~4.00 mg/mL. When the concentration was 4.0 mg/mL,the inhibition of tumor cell HepG-2 proliferation was nearly 50%,indicating that polysaccharides from bamboo leaves had potential anti-tumor activity.