A new salting-out extraction method, namely chelatometric salting-out extraction, was established for rapidly extracting flavonoids from Folium nelumbinis. Borax was used as a chelating agent and an ethanol/K2HPO4 system as the salting-out extraction system. The maximum flavonoid concentration in the top phase was observed at an ethanol concentration of 43.0% and an amount of salt of 2.45 g under the experimental conditions. The pH value of the system and extraction time had no obvious influence on the extraction efficiency of flavonoids. The results also showed that the extraction efficiency of flavonoids exceeds 90.4% at the first time extraction. Moreover, the antioxidant activities of flavonoids were evaluated by DPPH center dot radical assays.