ultrasonic power is an important parameter among ultrasonic variables.However,our previous study showed that ultrasonic power has a little effect on the yields of hesperidin from penggan peels.Moreover,it has been reported that the maximum ultrasonic power depended on the distance of ultrasonic irradiation surface.Therefore,to confirm this point,an experiment for ultrasound-assisted extraction (UAE) of heperidin from penggan peels at locally ultrasonic field was performed by response surface methodology (RSM).