A common used endpoint in bioassays testing the estrogenicity of chemicals including endocrine disruptors is the induction of egg yolk Precursor vitellogenin in male fish. Two marine fishes (Sebastes schlegeli and Paralichthys olivaceus) were exposed to the 17$eta$-estradiol(E2) to determine the vitellogenin production. Vitellogenin was measured in fish blood using SDS-PAGE and Densimetry. Results showed that exposure to E2 caused vitellogenin in male fish. Especially, vitellogenin levels in young fish were about 4 times higher than in adult fish, which means young fish are more sensitive to E2 exposure. And plasma vitellogenin in fish increased related to E2 concentration and exposure duration.