We investigated the evidence of gastric protection for ulcer and gastritis by Cinnamomi Ramulus (Cinnamomum cassia Blume, Geiji, CR) extract and its several constituents. CR ethanolic extract showed the potent antioxidant activity and cytotoxicity of Helicobacter pylori (H. pylori) and acid-neutralizing capacity. Especially, eugenol exerted a significant antioxidant activity and inhibited the colonization of H. pylori. In vivo test, eugenol and cinnamic acid significantly inhibited HCl/ethanol-induced gastric lesions and increased the mucus content though they didn't inhibit gastric secretion effectively. Taken together, eugenol and cinnamic acid, which were isolated from CR, exhibited the antioxidant activity in vitro and protective effect against gastric damage in vivo through stimulation of mucus secretion and so on. It suggested that they are useful as the neutraceuticals for gastritis.