Helicobacter pylori is a spiral, slow growing gram-negative microaerophilic bacterium. It has been shown to be the etiological agent of gastroduodenal diseases, such as chronic gastritis, gastric and duodenal ulcers, and gastric cancer. General culture condition of H. pylori is 5% $O_2$, 10% $CO_2$ and 100% humid atmosphere. We have compared proliferation protein expression profile of H. pylori incubated under normal microaerophilic (10% $CO_2$) and environment stress (4% $CO_2$, 18% $CO_2$) conditions. H. pylori cultured under environment stress displayed coccoid morphology and time-dependent decrease in proliferation. We have further compared the protein expression profiles of H. pylori under normal growing and environment stress conditions by a global proteomic analysis, which includes high-resolution 2-DE followed by matrix-assisted laser desorption/ionization time of flight and nanoelectrospray/tandem mass spectrometry. In total, 42 protein spots were found to be up- or down-regulated by more than 2-fold under environment stress conditions. Of the 42 protein spots processed, 27 spots were identified; they represented 19 genes, including 2 kinds of hypothetical proteins.