Objective To investigate the reinfection rate of Helicobacter pylori（H.pylori） in gastric mucosa by two measures of oral plaque control on patients, and to demonstrate the necessity and better method of plaque control on those patients. Methods 148 patients suffered gastritis or gastroduodenal ulcer were assigned into test group 1（54 patients）, test group 2（55 patients） and control group（39 patients）. 13C -urea breath test proved that there were no H.pylori in their gastric mucosa. Daily plaque control was used in test group 1, oral professorial interventions were added into test group 2, neither daily plaque control nor oral professorial interventions was conducted in control group. All patients were conducted 13C-urea breath test again after half a year to determine the reinfection rate of H.pylori in gastric mucosa. Results 5 patients were eliminated because of stopping mouthwash in the test group 1, 8 patients failed to control dental plaque in the test group 2. The infection rates of H.pylori in gastric mucosa of test group 1, test group 2 and control group were 67.3％, 19.1％, 82.1％, respectively. The infection rate of H.pylori of test group 2 was lower significantly than that in control group and test group 1（掊2＝ 33, P
