Objective: To optimally select the extraction technology of total flavonoids of Lycium barbarum leaves by ultrasonography and to determine the content of total flavonoids of L.barbarum leaves of different picked time. Method: The effects of four single-factors (including ethanol concentration

ethanol consumption

ultrasonic extraction time and temperature)on the extraction of total flavonoids of L. barbarum leaves have been studied.And the results of the orthogonal experiment were analyzed by variance analysis. Use the best extraction technology to determine the contents of total flavonoids in leaves of L.barbarum at different picked times. Result: The best single factor was determined and the best extraction of total flavonoids of L. barbarum leaves by ultrasonography with orthogonal experiment was optimized. The best extraction technology were as follows: using 65% ethanol as extractor with the ratio of material to liquid at 1 ∶60 and extraction for 35 min in 70 ℃. Conclusion: By comparing the contents of total flavonoids in leaves of L. barbarum at different picked time

the contents of total flavonoids in leaves were decreased with the leaves growing. It is conclude that the best picked time of L. barbarum is the middle of May.