In this paper,the secondary precipitates of soy sauce were prepared by natural precipitation,centrifugation,cooling,ultrasonic,and cooling-ultrasonic coupling methods.Their solubilities,proximate indices and amino acids composition were studied comparatively.Meanwhile,hierarchical cluster analysis was conducted to analyze the differences of amino acids composition in the above secondary precipitates.Results showed that proteins in the above precipitates could not be re-dissolved in acidic buffers(pH<7.0).The content of protein in precipitate prepared by cooling-ultrasonic coupling method was higher than that in precipitates prepared by other methods.Meanwhile,its amino acids composition was obviously different from those of the other precipitates.The cooling-ultrasonic coupling method was more scientific and quick for secondary precipitate preparation.