The diagnosis of RGERD in patients typically involves 24-hour esophageal pH monitoring, but due to its invasiveness and low patient compliance, new screening methods are needed. In this study, a lactulose breath test (LBT) was conducted to detect the growth of small intestine bacteria (SIBO) and explore the potential relationship between LBT and RGERD to identify a new treatment method for RGERD. A total of 178 patients with gastroesophageal reflux were enrolled from June 2020 to December 2022 in the Gastroenterology Department, Building 3, the First Affiliated Hospital of Kunming Medical University; these patients included 96 patients with nonrefractory GERD (NRGERD) and 82 patients with RGERD. The Gerd Q score, reflux symptom index (RSI) score, gastroscopy results, clinical symptoms, and other related indicators were collected. Statistical methods were used to analyze the gathered data. The incidence of acid reflux and heartburn in patients with RGERD was significantly greater than that in patients with NRGERD (67.10% vs. 42.70%, P<0.01 and 65.00% vs. 34.40%, P<0.01). The CH4 values of patients with RGERD were significantly greater than those of patients with NRGERD at each time point, and there was a correlation between the CH4 values at 60 min and RGERD (P<0.05). For patients with RGERD, the incidence of abdominal pain, acid regurgitation, and heartburn was greater in the CH4-positive group than in the CH4-negative group (61.90% vs. 57.50%, 69.05% vs. 65.00%, 69.05% vs. 57.50%, P>0.05). The incidence of nausea was also greater in the CH4-positive group than in the CH4-negative group (61.90% vs. 35.00%, P<0.05). Increased CH4 levels are correlated with RGERD. In addition, patients with RGERD may develop SIBO after long-term use of PPIs, and interventions involving SIBO could provide new ideas for the treatment of RGERD.