Interferon regulatory factor (IRF) family is a transcription factor family which plays an important role in the regulation of natural immunity and immune cell differentiation. IRF7 is important to regulate the response of type I interferon (IFN) to viral infection. Thus, more researches of the characteristic and functions of IRF7 should be done to get better understanding of the mechanisms underlying immune reactions. Here, the characterization of full-length cDNA of IRF7 was reported from miiuy croaker. Gene characterization analysis of mmiIRF7 showed conservative with other fish and inferred that the difference of tryptophan residues in IRF7 may occurred in the period of fish-specific genome duplication (FSGD) or earlier. Syntenic analysis of IRF7 showed that fish IRF7 had more highly conserved synteny than the higher vertebrates IRF7. Luciferase reporter assays result showed the ability of mmiIRF7 for activation of IFNα, IFNβ, IFNγ and ISRE luciferase reporter. In this study, we systematically and comprehensively analyzed evolution and function of mmiIRF7, which will provide the basis for future research on fish IRF family.