Pattern recognition receptors can recognize pathogens, and then cells are induced to produce pro-inflammatory cytokines and interferon by multiple signaling pathways. Nevertheless, excessive inflammation disrupts immune homeostasis, thereby inducing autoimmune and inflammatory diseases. Thus, the regulation of immune responses is extremely important for host to keep homeostasis. In this study, we found that miR-19a plays a negative regulator in MyD88-mediated NF-κB signaling pathway by targeting MyD88 in miiuy croaker. Furthermore, over-expression of miR-19a in macrophages suppresses the expression of MyD88 and its downstream signaling genes of IRAK1, IRAK4 and TRAF6, whereas, the inhibitor of miR-19a has opposite effect. This study can increase our knowledge and help us to furthermore understand miRNAs regulatory mechanism in teleost fish.