The best season for picking Brasenia schreberi was determined by studying the content of polyphenols and antioxidant capacity of B. schreberi at different picking periods.Ultraviolet spectrophotometry was used to determine the content of polyphenols in B. schreberi.DPPH,ABTS and FRAP methods were used to study the in vitro antioxidant activity of the extracts.The results showed that the highest polyphenol content in June was 28.045±1.654 mg/g,followed by 12.796±2.492 mg/g in October,and the lowest was 16.342±1.198 mg/g in August.B. schreberi in different picking periods The extracts all have antioxidant activity.This research can provide necessary data foundation and industry guidance for the process optimization and product quality supervision of B. schreberi in different picking periods.