Abstract: The method of ultrasonic-assisted extraction of proteins from Cordyceps militaris were optimized by response surface methodology,and the amino acid composition and nutritional value of the extracted C. militaris proteins were analyzed. The optimal conditions for the ultrasonic-assisted extraction of proteins were as follows：solid-liquid ratio of 1∶50,pH of 8.57,and ultrasonic at 150 W for 30 min,then the ultrasonic wave was turned off,the mixture was further stirred at 35℃ and extraction was conducted for 72 min. Under these conditions,the extraction rate of proteins reached 85.6%,which was 1.68 times of the non-ultrasound control group,and the relative error with the model prediction value was ±0.77%. Under the optimal conditions,the ratio of essential amino acids to total amino acids of C. militaris proteins was 44.4%,and the ratio of essential amino acids to non-essential amino acids was 79.84%,which was higher than the recommended values by the World Food and Agriculture Organization（FAO）and the World Health Organization（WHO）. It indicates that the extracted C. militaris proteins had high nutritional value,providing a reference for the efficient extraction of C. militaris proteins and the development of health food from C. militaris.

Key words: Cordyceps militaris, protein, ultrasonic-assisted, response surface, amino acid analysis