Proteins were extracted from three economic shellfish (Scallop, Clam and Abalones) by novel isoelectric solubilization/precipitation at different pH conditions. The compositions and characteristics of three shellfish protein isolates were then analyzed. The results showed that the optimal pH for alkali extraction are pH 12 and the optimal pH for acid precipitation of scallops, clam and abalone is 5.1, 5.1 and 4.8 respectively. The crude protein content of the three proteins isolates are all above 80% (dry basis). And the solubility of three shellfish protein isolates showed a trend of first decrease then increase from acidic to alkaline pH (2.0-13.0). The results of differential scanning calorimetric(DSC) analysis showed that the major endothermic peaks for Scallop protein isolates(SPI)、Clam protein isolates (CPI) and Abalones protein isolates (API) were centered at approximately 57.0, 61.6 and 63.6 ℃, respectively. SDS-PAGE showed that the three protein isolates are abundant in Myosin HC (MHC), Myosin LC (MLC) and actin with some degradation of myofibrillar proteins during the extraction process. The contents of all essential amino acids in the three protein isolates met FAO/WHO/UNU recommendations for adults and infants.Therefore, the three shellfish protein isolates are a high quality protein for human consumption. The results provide a theoretical basis for the application of shellfish protein isolate as a high quality nutritional protein in health food production industry.