In order to optimize the conditions for the ultrasound-extraction technology of total flavonoids from green tea,the Plackett-Burman design was introduced to evaluate the effects of five factors based on single factor test.Ethanol concentration,ratio of liquid to solid and extraction times were found to be the critical for the factors activity of total flavonoids extraction.The optimum conditions for extraction were obtained through Box-Behnken center-united experiment design and Response Surface Methodology...