The composition and biological activities of tea polysaccharides (TPS) obtained by traditional water extraction, boiling water extraction and enzymatic extraction were investigated. Boiling water extraction (100 °C for 2 h) was found to be the optimal method with higher yield of TPS (1.91%) consisting of higher contents of neutral saccharides (57.82%) and acid saccharides (26.95%) with lowest protein content (3.06%). TPS obtained by boiling water extraction exhibited a strong inhibitory effect on α-glucosidase with the inhibitory rate of 86.67%. The inhibitory effect of TPS on α-glucosidase increased with increasing neutral polysaccharides content in TPS. TPS obtained by boiling water extraction (50 μg/mL) had very strong proliferation effect on lymphocyte.