Abstract: By means of the vertical polyacrylamide gel gradient electrophoresis, four isozymes (EST, LDH, MDH and SOD) from five tissues (kidney, liver, eye, muscle and heart) of hybrid Tilapia were studied. And their locis and phenotypes were also analyzed. The results showed that four isozymes presented obvious tissue specificity. EST isozymes coded by seven locis′s genes; the protein bands of LDH isozymes were more than 5 which LDH phenotypes of most of the typical teleosts have; the phenotypes of both SOD and MDH had two types, mitochondria type and supernatant type, in hybrid Tilapia.