Abstract: Taking quinoa as the raw material, NaOH solution was used as solvent, ultrasonic-assisted thermo-alkaline technology was used to extract soluble protein from quinoa. The extraction temperature, extracting time, extraction solid-liquid ratio and ultrasonic power that affected the extraction rate of quinoa protein were optimized by single factor experiment and response surface experiment, and the solubility, emulsification and foaming activity of the extracted products were determined. The results showed that the optimal extraction conditions of quinoa protein were: Temperature 40 ℃, ultrasonic time 2 h, solid-liquid ratio 1:35 (g/mL) and ultrasonic power 400 W. The extraction yield ratio of quinoa protein reached 78.20%, which was basically consistent with the predicted value of regression model of response surface optimization test. The emulsifying and foaming properties of quinoa protein showed that 3.5% of quinoa protein had preferable emulsifying properties and emulsifying stability, solubility of 61.18%, emulsifying properties of 5.39 m²/g and emulsifying stability of 255.59 min; 3% of quinoa protein solution had superior foaming property and foam stability, foaming ability 101.0%, and foam stability 66.0%.