Objective: This study focused on improving the extraction rate and application of Mesona chinensis polysaccharide (MCP). Methods: MCP was obtained from fresh M. chinensis by thermally alkaline extraction, protein removal by trichloroacetic acid and purification by dialysis bag. The chemical structure was analyzed by ultraviolet and infrared spectrum scanning, X-ray diffraction and SEM scanning. The antioxidant activity was determined by in vitro antioxidant capacity, and the antibacterial activity was determined by antibacterial experiment. Results: The optimal extraction conditions of MCP were solid-liquid ratio of 1∶5.47 (g/mL), soaking time of 10.71 min, sodium bicarbonate concentration of 1.64%. Under the control of these conditions, the extraction yield of MCP was (7.57±0.63)%. The spectral analysis showed that MCP contained protein and uronic acid and was a pyranoside ring framework with β-glycosidic bond. The maximum scavenging rates of polysaccharides from M. chinensis on DPPH and ABTS free radicals were 66.35% and 79.63%, respectively, and the maximum absorbance of reducing power was 1.431; Antibacterial experiments showed that MCP inhibited the growth of Bacillus subtilis. Conclusion: The optimized extraction process is reasonable and feasible for MCP. The polysaccharide spectrum has obvious common characteristics and has good antioxidant ability and antibacterial ability.