Objective To investigate the correlation of Helicobacter pylori infection in the oral cavity and stomach, and correlation of Helicobacter pylori infection in the oral cavity and periodontitis. Methods 120 patients with chronic gastric diseases received 13C-urea breath test, Hp saliva test and periodontal examination. The correlation of Helicobacter pylori infection in the oral cavity and stomach, and correlation of Helicobacter pylori infection in the oral cavity and periodontitis were analyzed. Results The experiments showed that the positive rate of Hp in the oral cavity was 87.7% in stomach-Hp-positive patients, while the positive rate of Hp in the oral cavity was only 42.6% in stomach-Hp-negative patients, which was significantly lower (P