Herein, we found that serum concentration of superoxide dismutase 3 (SOD3) was significantly reduced inchildren with mycoplasma pneumonia (MP) infection. To study the roles of SOD3 in inflammatory regulationof MP infection, human A549 type II alveolar epithelial cells were stimulated with 10^7 CCU/ml of MP to buildMP infection in vitro. Secretion of pro-inflammatory cytokine interleukin (IL)-8 and tumor necrosis factor(TNF)-alpha were measured via enzyme-linked immunosorbent assay (ELISA) to assess the inflammatory responseof A549 cells. Levofloxacin (LVFX) was used as an anti-inflammatory drug while recombinant TNF-alpha wasused as an inflammatory promotor in MP-infected cells. Transcriptional activity of nuclear factor (NF)-kappa-B wasassessed by detecting protein levels of nuclear NF-kappa-B and cytoplasm NF-kappa-B using Western blot analysis. Ourdata suggested that the expression of SOD3 mRNA and protein, as well as content of SOD3 in culturedsupernatant, were time-dependently inhibited in MP-infected A549 cells. However, lentiviruses-mediatedSOD3 overexpression alleviated inflammatory response of MP-infected A549 cells, and prevented the uncleartranslocation of NF-kappa-B, as evidenced by obviously reducing the production of IL-8 and TNF-alpha in cell culturedsupernatant, as well as decreasing nuclear NF-kappa-B while increasing cytoplasm NF-kappa-B. Inspiringly, SOD3overexpression induced anti-inflammatory effect and the inactivation of NF-kappa-B was similar to that of 2 lg/mlof LVFX, but reversed by additional TNF-alpha treatment. Therefore, we can conclude that transcriptional activityof NF-kappa-B was the underlying mechanism, by which SOD3 regulated inflammatory response in MP infectionin vitro.