Abstract: The physicochemical properties and amino acid composition of Mytilus coruscus protein isolate which was extracted by isoelectric precipitation along with dephenolizing by ethanol/water and dialysis from mussel powder, a byproduct after lipid extraction of Mytilus coruscus were investigated. The protein isolate contains 93.8% protein and abundant essential amino acids, about 36% of total amino acids, without significant change before or after extraction, especially lysine, leucine, phenylalanine, threonine and valine which satisfy the FAO/WHO recommendation. Good solubility of Mytilus coruscus protein isolate was observed. The physicochemical properties of Mytilus coruscus protein isolate such as water holding capacity, oil absorption and foaming ability were better than soybean protein isolate and egg protein while its emulsifying ability was not good as soybean protein isolate and egg protein. The present results indicated that Mytilus coruscus protein isolate could be used as a protein resource. The comprehensive utilization of the byproduct after lipid extraction of Mytilus coruscus could be greatly enhanced through the further study on the optimization of the extraction method and its physical and chemical characteristics.