The protein composition and distribution of cadmium in different protein composition were investigated in Pteria penguin.The contents of cadmium in different protein compositions which were separated from Pteria penguin were determined by atomic absorption spectrometry (AAS).Molecular weight distribution of different protein were determined by sodium dodecyl sulfonate-polyacrylamide gel electrophoresis (SDS-PAGE) and high performance size exclusion chromatography (HPSEC) chromatogram.In the present study,three protein compositions were separated from whole viscera of Pteria penguin,and content of each protein component in total protein were 27.3% sarcoplasmic protein,23.1% myofibrillar protein,50.0% total matrix protein (there were 10.3% of acid soluble matrix protein,39.7% of acid insoluble matrix protein,22.1% of alkali soluble matrix protein and 27.9% of alkali insoluble matrix protein in total matrix protein).There were a large respective divergence in the molecular weight distribution of sarcoplasmic protein,myofibrillar protein and acid/alkali soluble matrix protein,with sarcoplasmic proteins and myofibrillar protein exhibiting wide molecular weight distribution range of 20-200 ku and complex compositions,and acid/alkali soluble matrix protein having simple composition,while there were complex compositions of sarcoplasmic proteins and alkali soluble matrix protein and simple compositions of myofibrillar protein and acid soluble matrix protein in the low molecular weight range of 2-20 ku.The distribution of cadmium in three major protein compositions including total matrix protein,sarcoplasmic protein and sarcoplasmic protein exihibted a significantly positive correlation with contents of proteins (r=0.998 5),while the distributions of cadmium in different matrix protein had a significantly negative correlation with contents of proteins(r=0.996 4).The results suggested that cadmium did not evenly distribute in protein of Pteria penguin,but selectively combined with different protein components,and cadmium can not be dissociated from protein under mild extraction conditions,but it was dissociated from protein under extreme pH conditions.