-Ｏｂｊｅｃｔｉｖｅ　To investigate effects of hyperbaric oxygen (HBO) preconditioning on lipopolysaccharide (LPS)-induced damage to human alveolar typeⅡepithelial cells via extracellular regulated protein kinases 1/2(Erk1/2) signal pathway.　Methods　A549 cells at the logarithmic growth phase were seeded in plates (density 0.5×106 cells/ml, 2 ml/well), a total of 147 wells. The cells were randomly divided into 7 groups (n=21): C group, LPS group, HBO+LPS group, PD+HBO+LPS group, HBO group, PD group and PD+LPS group. LPS was stimulated by LPS 1 mg/L for 4 h. After LPS exposure, the culture of HBO+LPS, PD+HBO+LPS groups were treated with 100 kPa HBO for 1 h. The cultures in PD+HBO+LPS, PD and PD+LPS groups were treated with PD98059 (30 μmol/L) to inhibit phosphorylation of Erk1/2, but C group without any treatment. The effects of apoptosis were assessed by Annexin V-FITC/PI assay. The expressions of cytoskeleton filament actin (F-actin) were assessed by immunofluorescence assay. ATP content was assessed by fluorescein-luciferase assay kit. The expressions of phosphorylational Erk1/2 were assessed by Western blot measurement.　Results　Compared with C group, there were significant increases of apoptosis, recombining of F-actin, and expression in phosphorylation of Erk1/2, Bid, Bim, Puma but decrease of ATP content in LPS group (P<0.05). Compared with LPS group, there were significant decreases of apoptosis, recombining of F-actin, ATP content and expression in Bid, Bim, Puma but decrease of phosphorylation of Erk1/2 in LPS group (P<0.05), while the neuroprotection of HBO was partially restored by PD98059 in PD+HBO+LPS group (P<0.05).　Conclusions　The protection of HBO preconditioning on LPS-induced damage to human alveolar typeⅡepithelial cells may be related with stabilization of mitochondrial function via Erk1/2 signal pathway.