Abstract: 【Objective】 To explore the expression pattern of Trachinotus ovatus JunB gene(ToJunB) in embryonic development, and lay a foundation for exploring the mechanism of JunB on embryonic development process.【Method】 RT-PCR was used to amplify the encoding region(CDS) sequence of the ToJunB gene, and the bioinformatics analysis was carried out with online softwares such as ProtParam, NetSurfP 2.0, TMHMM, SignalP, PSORT and NetNGlyc 1.0. Real-time fluorescence quantitative PCR was used to detect the expression of ToJunB mRNA in 17 bryonic development stages of T. ovatus(zygote, 2-cell embryo, 8-cell embryo, 16-cell embryo, 32-cell embryo, 64-cell embryo, multicellular stage, blastula stage, early gastrula stage, gastrula stage, late gastrula stage, embryo formed stage, optic vesicle stage, otocyst vesicle stage, heart pulsation stage, formation of eye lens and hatching stage).【Result】 The ToJunB gene cloned from embryonic tissues of T. ovatus was 1777 bp in length, consisted of 344 bp 5' end non-coding region(5'- UTR), 954 bp open reading frame(ORF) and 479 bp 3' end non-coding region(3'-UTR), encoding 318 amino acid residues, its protein molecular weight was 35.03 kD, theoretical isoelectric point (pI) was 8.26, it was alkaline. The total average hydrophobic index(GRAVY) was -0.567, indicating that it belonged to hydrophilic protein. ToJunB protein had no transmembrane structure, no signal peptide sequence, and a potential glycosylation site at amino acid 39, 129, 168. The ToJunB protein mainly existed in the nucleus, belonging to asecretory protein. In the secondary structure, α- helix and extended strand accounted for 35.67% and 14.33%, random coil accounted for 50.00%. The phylogenetic trees based on amino acid sequence similarity of JunB indicated that the closest genetic distance with T. ovatus and Serio lalalandi dorsalis. They both were Hericidae, Perciformes. The relative expression of ToJunB gene was higher in the early stage of embryonic development(from the zygote to the early gastrula stage), reached the highest value in the gastrula stage, and kept low value in the late stage of embryonic development(from the late gastrula stage to the hatching stage). The expression level of ToJunB gene in the 10 developmental stages from zygote to early gastrula was extremely significantly higher than that from the late gastrula to the early hatching stage(P<0.01).【Conclusion】 The relative expression of ToJunB gene is higher from the zygote to the early gastrula stage, reaches the highest value in the gastrula stage and then reduces rapidly, and keeps low value from the late gastrula stage to the hatching stage. The result show that JunB gene plays an important role in the cell division and proliferation in embryo development of T. ovatus.