Abstract: Composite surfactants of PEG1000 and PVP30000 and definite amounts of (NH4)2SO4 and H2O were chosen experimentally as components of the binary aqueousphase extraction system.The volume ratio between PEG 1000 and PVP 30000,the acidity of the extraction solution and the amount of (NH4)2SO4 used,which are the influential factors to the phase separation,were studied and the optimized conditions found were as follows:① VPEG 1000/VPVP 30000=2.00 mL/2.00 mL;② acidity:pH 6.0,using B.R.buffer;③ amount of (NH4)2SO4 added:1.5 g.Rutin in mulberry leaves was extracted with the binary aqueous-phase extraction system (BAPES) quantitatively into the PEG 10000-PVP 30000 phase by two extractions and determined UV-spectrophotometrically in that phase at 375 nm.Values of RSD and recovery found were ≤3.8% and 96.5% respectively.Results of interference test showed that the selectivity of this method was also acceptable.The use of ultrasonic wave for shaking of the extraction mixture showed higher efficiency than the conventional soxhlet method.