Objective To investigate the effects of exogenous nitric oxide(NO) on NFκB activity and TNF-α production of U937 induced by LPS. Methods U937, which was induced by PMA and became mature, was divided into 4 groups: normal control without any treatment, LPS group treated with 10 ng/ml LPS and 100 ng/ml rhLBP, low-dose exogenous NO(SNP) group treated with LPS and rhLBP and 50 mol/L SNP, and high-dose SNP group treated with LPS and rhLBP and 500 mol/L SNP. The activity of NFκB was evaluated by immunochemical staining and image analysis and Western blotting. The concentration of TNF-α in the supernatant of U937 cell culture was detected by ELISA. Results The activity of NFκB and the concentration of TNF-α in SNP treated groups were significantly lower than those in LPS and LBP treated group, but higher than those in control group. Conclusion LPS can activate NFκB through LBP and induce the release of TNF-α. SNP can reduce the release of TNF-α, which may be through inhibiting the activation of NFκB. Exogenous NO might have a potential value in the prevention and treatment of acute lung injury or sepsis.