Objective To investigate if microRNA(miRNA)-155 intensifys hypoxic-ischemic brain injury in neonatal rats by regulating nucleotide-binding oligomerization domains 1 (NOD1)/ nuclear factor κB (NF-κB) signaling pathway.   Methods Forty neonatal male rats were selected and divided into four groups with 10 rats in each group. They were sham operated group, hypoxic-ischemic group (HI group), negative control group (NC antagomir group), miRNA-155 inhibition group (miRNA-155 antagomir group). After 10% chloral hydrate (400 mg/kg) anesthesia, the left brain of rats was taken and the water content of brains tissue were measured. Histopathological changes of hippocampus and cortex were observed under light microscope by HE staining. Western blotting method  was used to detect the expression levels of NOD1, NF-κB p65, NF-κB p50, phosphorylated NF-κB p65 (p-NF-κB p65) and p-NF-κB p50 in brain tissues of rats in each group. The mRNA expression levels of miRNA-155, NOD1, NF-κB p65 and NF-κB p50 in brain tissue and serum of rats were detected by Real-time PCR.  Results  Compared with the sham operated group, the brain water content of neonatal rats in HI group and NC antagomir group increased significantly, and that in miRNA-155 antagomir group decreased significantly (P<0.05). The hippocampal cells in sham operated group were arranged neatly, with clear and complete cellular structure and hierarchy, no vacuoles and no edema in the stroma were observed. The hippocampal cells in HI group and NC antagomir group arranged disorderly, forming vacuoles, glial cell proliferation, cell gap widening, edema and more necrotic cells were observed. In the group of miRNA-155 antagomir, brain edema was significantly alleviated, hippocampal cell disorder was improved, and the number of necrotic cells was reduced. Compared with sham-operated group, the protein expression levels of NOD1, p-NF-κB p65 and p-NF-κB p50 in HI group and NC antagomir group were significantly higher, while the expression levels of miRNA-155 antagomir group were significantly lower than those in HI group and  NC antagomir group (P<0.05). The expression level of NOD1 in brain tissue and serum of neonatal rats in HI group and NC antagomir group was significantly higher than that in sham operated group. The expression level of NOD1 in miRNA-155 antagomir group was significantly lower than that in HI group and NC antagomir group (P<0.05), but there was no significant difference in the expression levels of NF-κB p65, NF-κB p50 among the groups (P>0.05).  Conclusion MiRNA-155 can promote hypoxic-Ischemic brain injury in neonatal rats by regulating NOD1/NF-κB signaling pathway. Its mechanism may be related to the activation of NOD1 signaling pathway by miRNA-155, the phosphorylation of downstream NF-κB, and increased brain inflammation in neonatal rats with hypoxic-ischemia.