Abstract: In order to make high-value use of the by-products in Trachinotus ovatus processing,the optimal extraction technology of alkali-soluble protein from the by-product in Trachinotus ovatus processing was determined by alkali extraction and orthogonal test,and the related properties of the extracted alkali-soluble proteins were analyzed. The results showed that the optimal extraction conditions for alkali-soluble protein were:Alkali-extraction concentration was 0.3 mol/L,ratio of solid-liquid was 1:8 g/mL,alkali-extraction temperature was 50 ℃,alkali-extraction time was 70 min,and the extraction rate of alkali-soluble protein reached 83.71%. The pI of alkali-soluble protein was 4.6,the solubility reached its peak when the pH was 9.0,oil absorption was 5.5 mL/g,water absorption was 1.85 mL/g,emulsification was 43.44%,foaming was 75.33%,and foaming stability was 37.5%. The amino acid composition analysis showed that the contents of essential amino acids(except tryptophan)and umami amino acids were 47.84% and 34.23%,respectively. SDS-PAGE showed that the alkali-soluble protein molecules were mainly distributed in four bands of 90,70,65,and 44.3 kDa,which would provide a certain technical basis for further processing of side product of Trachinotus ovatus.