Objective:To study reflux characteristics of patients with endoscopic negative heartburn and their manifestation under probe-based confocal laser endoscopy (pCLE) based on the Rome Ⅳ standard.Methods:Thirty-six endoscopic negative outpatients with typical heartburn at the Department of Gastroenterology of the Second Affiliated Hospital of Baotou Medical College from September 2020 to March 2021 were included, and underwent 24-hour multichannel intraluminal impedance-pH monitor and pCLE. According to Rome Ⅳ diagnostic process, patients were divided into non-erosive reflux disease (NERD) group ( n=16), reflux hypersensitivity (RH) group ( n=8) and functional heartburn (FH) group ( n=12). The Gerd-Q scale score, 24-hour pH monitoring results and microstructure changes under pCLE were compared among the three groups. Results:There was no significant difference in the total score, positive symptom score, negative symptom score or positive influence score of Gerd-Q scale among the three groups ( P>0.05). DeMeester score [28.45 (20.08, 34.53)] and acid reflux times (24.88±9.05) in the NERD group were significantly higher than those in the RH group [7.30 (3.90, 11.38), P<0.001; 13.63±5.76, P=0.003] and FH group [6.90 (4.80, 9.73), P<0.001; 7.42±8.32, P<0.001]. But there was no significant difference between the RH group and the FH group ( P>0.05). The diameter of intra-papillary capillary loop (IPCL) (18.68±2.12 μm) and dilation of intercellular space (3.95±0.97 μm) in the NERD group were significantly higher than those in the RH group (13.91±1.99 μm, P<0.001; 2.97±0.55 μm, P=0.006) and FH group (13.83±2.00 μm, P<0.001; 2.31±0.54 μm, P<0.001), but there was no significant difference between the RH group and the FH group ( P>0.05). The number of IPCL in the NERD group, RH group and FH group were 2.0 (1.00, 2.75), 2.0 (1.00, 2.75) and 1.5 (1.00, 2.00), respectively with no significant difference ( P=0.697). Conclusion:Gerd-Q scale is not suitable for differential diagnosis of patients with endoscopic negative heartburn. Compared with functional esophageal diseases (RH and FH), acid reflux and mucosal microstructure changes are of more important pathogenic significance in NERD.