The present invention relates to a method for separating protein from food by using an iso-electric point precipitation, comprising: obtaining a protein extract by adjusting pH of a raw material food in a media; precipitating the protein by adjusting pH of the protein extract to an iso-electric point of the desired protein; and recovering the protein precipitated after separating a protein filtrate through centrifuging the precipitated protein; in which the method may further include a heat-precipitation of the protein by heating the protein extract or the protein filtrate to 60~145 °C. The protein obtained in high yield according to the above method can be used as a food additive or a food nutritional enhancer.