Abstract: This study aimed to obtain the optimum conditions for the extraction of free amino acids from the meat of Chinese Mitten Crab(Eriocheir sinensis),the ultrasonic time,ultrasonic temperature,ultrasonic power,extraction times and liquid-to-liquid ratio were studied by the orthogonal test. The results showed that,the effects of factors on the extraction yield of amino acids were in the descending order of solid-to-liquid ratio>number of extraction cycles>ultrasonic time>temperature. The optimum level of male crab was determined by ultrasonic power 200 W,extraction temperature 40℃,ultrasonic ratio extraction 1:30 (g/mL)for 7 min,extraction times was 3.Under these conditions,the actual extraction yield of free amino acids for male crab was(26.227±0.244) mg/g. The optimum level of female crab was determined by ultrasonic power 200 W,extraction temperature 20℃,ultrasonic ratio extraction 1:40 (g/mL)for 5 min,extraction times was 2.Under these conditions,the actual extraction yield of free amino acids for female crab was(25.101±0.135) mg/g.