Objective To investigate the role of ineffective esophageal motility (IEM) in non-erosive acid reflux related diseases, and the influence of the fourth edition Chicago classification (CC v4.0) on the diagnosis of IEM. Methods From January 2018 to January 2020, 63 patients with acid reflux related symptoms who underwent gastroscopy and showed no abnormal changes in esophageal mucosa or structure, and underwent high resolution esophageal manometry (HRM) and 24-hour esophageal pH monitoring in the Department of Gastroenterology of Beijing Friendship Hospital were included in the case-control study. According to the HRM results, the third edition Chicago classification standard (CC v3.0) and CC v4.0 were used to divided patients into IEM group and normal dynamic group. The HRM results, 24-hour esophageal pH monitoring results and final diagnosis of the two groups under the two editions of Chicago classification standard were mainly compared and analyzed. Results Among the 63 patients, there were 14 cases of non-erosive gastroesophageal reflux disease (NERD), 19 cases of reflux hypersensitivity (RH), and 30 cases of functional heartburn (FH). When using CC v3.0, there were 20 cases in the IEM group, including 9 cases of NERD, 5 cases of RH and 6 cases of FH, and 43 cases in the normal dynamic group, including 5 cases of NERD, 14 cases of RH and 24 cases of FH. When using CC v4.0, there were 16 cases in the IEM group, including 7 cases of NERD, 4 cases of RH and 5 cases of FH, and 47 cases in the normal dynamic group, including 7 cases of NERD, 15 cases of RH and 25 cases of FH. When using CC v3.0, compared with the normal dynamic group, the acid exposure time (AET) of the IEM group was significantly higher [3.45 (1.55, 6.40)% VS 1.20 (0.40, 2.30)%, Z=-2.940, P=0.003], the DeMeester score was also significantly higher [13.8 (5.8, 21.4) VS 5.3 (2.9, 10.0), Z=-2.851, P=0.004], the lower esophageal sphincter pressure (LESP) [10.15 (7.52, 13.65) mmHg (1 mmHg=0.133 kPa) VS 15.40 (11.20, 21.60) mmHg, Z=-3.241, P=0.001], 4-second integrated relaxation pressure (4sIRP) (3.79±0.57 mmHg VS 6.05±0.50 mmHg, t=2.727, P=0.008), and distal contraction integral (DCI) [334.65 (208.25, 438.92) mmHg·s·cm VS 1 258.70 (919.00, 1 750.10) mmHg·s·cm, Z=-6.305, P<0.001] were significantly lower than those of the normal dynamic group. When using CC v4.0, AET and Demeester scores in the IEM group were also significantly higher than those in the normal dynamic group (both P<0.05), and LESP, 4sIRP and DCI were also significantly lower than those in the normal dynamic group (all P<0.05). In addition, upper esophageal sphincter pressure was significantly lower than that in normal dynamic group [34.60 (21.50, 48.05) mmHg VS 49.67 (36.75, 61.10) mmHg, Z=-2.140, P=0.032]. Conclusion IEM is associated with impaired anti-reflux barrier function and esophageal acid exposure in patients with non-erosive acid reflux related diseases. Compared with CC v3.0, CC v4.0 can reduce the heterogeneity of IEM patients to some extent.