Abstract: Objective To study the value of 24 hours dual-probe monitoring in patients with pathological gastroesophageal acid reflux (GER). Methods Retrospective investigation and analysis were carried out in 51 patients with GER symptoms in our hospital from August 2011 to September 2012. All patients had underwent 24 hours dual-probe pH monitoring of esophagus and they were divided into with both low and upper-esophageal reflux group (n=20), with upper-esophageal reflux only group (n=2), with low-esophageal reflux only group (n=9) and without any esophageal reflux group (n=20) according to test results. Positive rates of pathological gastroesophageal acid reflux were compared between one-probe and dual-probe pH monitoring for 24 hours. The potential causes for patients had upper-esophageal reflux only and the relationship between low and upper-esophageal reflux were analyzed. Results Of the 9 patients with upper-esophageal reflux only, 8 cases were detected by gastroscopy and/or High-resolution manometry (HRM) examination, including 1 just case complained of globus sensation without obvious regurgitation and heartburn symptoms, and the rest 7 patients complained of reflux and heartburn: 2 patients with hiatal hernia, 2 with achalasia, 1 with Nutcracker esophagus, 1 with duodenal ulcer (DU) and 1 operated gastroscopy only turning out with no pathological changes. The upper-esophageal reflux was more serious when patients had both upper-esophageal reflux and low-esophageal reflux. The percent and total amount of time of the esophageal pH< 4 in the upright and supine positions and DeMeester score were significantly increased (P< 0.05), while there showed no significant differences in maximum reflux time (P> 0.05). Both upper and low esophageal reflux were related to age. Conclusion 24 hours dual-probe monitoring may be useful in diagnosing GERD with apparent symptoms and no reflux being found by single-probe monitoring of gastroesophageal. Moreover, the pathogensis, morbidity and severity of LPR are closely related to GERD and 24 hours dual-probe monitoring is helpful for the research.