In the innate immune responses in host protection, pattern recognition receptors are involve in a variety of sensing mechanisms to recognize and counter pathogen invasion. Recently, a resident endoplasmic reticulum adaptor, stimulator of interferon genes (STING) protein, also called MPYS, ERIS and MITA, has been indicated to play a critical role in innate immune responses. In this study, bioinformatics and functions of MITA from miiuy croaker (mmiMITA) were characterized. MmiMITA was ubiquitously expressed in the detected tissues of miiuy croaker and the highest expression in liver. Moreover, the expressions were dramatically upregulated in liver, spleen and kidney after stimulation with poly(I:C). Meanwhile, the expressions analysis of mmiMITA at the transcriptome database further prove that upon different stimuli, mmiMITA is most sensitive to the stimulation of poly(I:C) in vivo. Furthermore, the immunofluorescence of mmiMITA shows in the cytoplasm of Hela cells. Overexpression of mmiMITA can activate NF-κB reporter gene, it implying that mmiMITA might act as an important role in immune responses by activating NF-κB to induce the production of pro-inflammatory cytokines. The research of mmiMITA will enrich the information of teleost fish MITA and the functional experiments also will be helpful for researching about fish immune systems in the future.