Abstract: The extraction of total flavoniods from Neosinocalamus affinins leaves by microwave-assisted extraction was carried out, and the optimal extraction conditions was studied, such as extraction temperature, extraction time and liquid-to-solid ratio, by response surface analysis (RSA) based on single factor tests. The results showed that the optimal extraction conditions were as follows in the presence of 80% ethanol as solvent, extraction temperature 70℃, extraction time 10. 5minutes and liquid-to-solid ratio 34mL/g. Under the optimal conditions, the yield of total flavoniods from Neosinocalamus affinins leaves reached 1. 381%. Antioxidant activities were evaluated by using 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical in vitro. The IC50 was 141. 5mg/L, and the result showed that the DPPH radical scavenging activity of flavonoids was stronger that of DPPH.