ObjectiveTo investigate the effects of probiotics combined with bismuth quadruple therapy （BQT） on clinical efficacy、gastrointestinal adverse reactions and intestinal flora in Helicobacter pylori （HP） positive patients. MethodsThe patients who were positive for HP from May 2023 to July 2023 in the department of gastroenterology of Shanghai first people's hospital were randomly divided into2 groups with 40 people in each group. The probiotic group was given 2 weeks of quadruple therapy with probiotics and standard BQT， followed by 4 weeks of oral probiotics after quadruple discontinuation. The placebo group was given 2 weeks of probiotic placebo and standard BQT， followed by 4 weeks of oral probiotic placebo. 13C urea breath test was used to evaluate the clinical efficacy， gastrointestinal symptoms rating Scale was used to evaluate the gastrointestinal adverse reactions of patients before and after the intervention， and microbial diversity 16S rDNA sequencing technology was used to detect the level of intestinal flora of patients before and after the intervention. ResultsThere was no significant difference in the eradication rate between the two groups （P>0.05）. Before the intervention， there was no significant difference in the scores of the gastrointestinal symptom rating scale between the probiotic group and the placebo group. After the intervention， patients in the probiotic group had significantly lower pain scores on acid reflux （1.10±0.30 vs 1.35±0.53， P<0.05） and stomach or abdominal hunger than in the placebo group （1.07±0.26 vs 1.30±0.52， P<0.05）. Through the before-and-after comparison of the probiotic group， the scores of abdominal pain （1.24±0.44 vs 1.58±0.71， P<0.05）， stomach or abdominal hunger （1.07±0.26 vs 1.27±0.45， P<0.05） and dry and hard stool （1.24±0.49 vs 1.48±0.75，P<0.05） were significantly lower in the probiotic group than before the intervention in the probiotic group. ConclusionProbiotics combined with BQT can improve the gastrointestinal adverse reactions and intestinal flora disorders in the process of quadruple drug therapy， but it does not improve the eradication rate of HP.