Objective:To study the effect of NF-?B “decoy” oligodeoxynucleotides on nitric oxide synthase expression in LPS-induced mouse macrophages. Methods: Mouse macrophage cell lines J774.1 were cultured with LPS and liposome-mediated oligodeoxynucleotides, and the level of nitric oxide and inducible nitric oxide synthase were measured in the different culture fluids. RNA was extracted from macrophages, and the mRNA expression of macrophages inducible nitric oxide synthase was observed by RT-PCR. Results: NF-?B “decoy” oligodeoxynucleotides decreased the activity of inducible nitric oxide synthase in LPS-induced macrophage, and inhibited the generation of nitric oxide. The level of nitric oxide and inducible nitric oxide synthase did not change in control group. Conclusion: NF-?B “decoy” oligodeoxynucleotides inhibit the expression of inducible nitric oxide synthase in LPS-induced macrophages, reducing the amount of nitric oxide, which is probably due to specific inhibition of the binding sites of activated nuclear factor-kappa B.