Three types of Paphia undulata protein including myosinogen,myofibril protein and matrix protein were isolated and their molecular weight distribution and function characteristics were investigated in this paper to make full use of protein resources from Paphia undulata.Results indicated that the proportions of myosinogen,myofibril protein,matrix protein and nonprotein nitrogen(NPN) in Paphia undulata total protein were 31.2%,45.42%,20.69%,and 1.67%,respectively.Analysis results of SDS-PAGE electrophoresis showed that myosinogen strips distributed widely between 200 kDa and 29.0 kDa,and Myofibril protein strips mostly ranged from 66.4 to 200kDa and from 29.0 to 38.0kDa,and Matrix protein had obvious banding in 190kDa,97kDa,44kDa and 29kDa.Under the same protein concentration,the turbidity of myosinogen and myofibril protein rose,while the solubility reduced with the temperature increasing.Effects of pH on the solubility and turbidity of myosinogen were not obvious,and the solubility was above 71% under pH ranging from 3.5 to 9.5.However,effects of pH on the solubility and turbidity of myofibril protein were obvious.The solubility was lowest,while the turbidity was at its maximum at pH 4.5.Turbidity of myofibril protein rose,while solubility declined with ionic strength declining.