Abstract: Extraction and separation of Phaseolus coccineus L.protein by two-phase aqueous systems was investigated using Plackett Burman design, steepest ascent design and central composite design.Firstly, PB design was applied to identify temperature and pH value as the most significant of 7 factors influencing the extraction.Then the center points of the two factors were determined based on steepest ascent design.Then the optimization of the two factors was carried out by using central composite design.The results showed that the best extract conditions were as follows:the mass fractions of PEG600 15%, the mass fractions of (NH4) 2SO4 20%, the mass fractions of NaCl 0.05%, sample volume added 4mL, pH 7, temperature at 35℃ and time by 90 minutes.Under such conditions, the extraction rate was 43.69%.The extraction rate was in good agreement with the predicted one of 42.85%.In conclusion, the optimized process had good reliability.