Background Little attention has been paid to the expression of heat shock protein 27 (HSP27) in patients with reflux esophagitis (RE), and few studies of the importance of HSP27 in esophagitis have been carried out in animal models.This study aimed to explore the expression of HSP27 in the esophageal tissue of rats with RE. Methods Eighty female Wistar rats were randomly divided into experimental groups A and B and control groups C and D (n=20 in each group). To establish RE, rats in the two experimental groups received pylorus and forestomach ligations,while rats in the control group received gastrostomy and gastric perforation repair. The rats in groups A and C were sacrificed 7 days after surgery, and the rats in groups B and D were sacrificed 14 days after surgery. In groups A and B,10 and 8 rats were diagnosed with RE by pathological examination, respectively (they were included in groups A' and B',respectively). The histopathological diagnosis of all the lower esophageal tissues in groups C and D was normal and 20normal specimens were randomly selected for groups C and D' with 10 specimens in each group. Macroscopic and microscopic esophagitis scores were assessed for the specimens in groups A' and B'. Lower esophageal tissues were collected from groups A', B', C, and D', and paraffin-embedded slices were made using part of the tissues. The expression of HSP27 in the tissues was detected using the two-step streptavidin-peroxidase immunohistochemical method. Some collected tissues were frozen, and expressions of HSP27 mRNA were detected using fluorescence quantitative polymerase chain reaction (FQ-PCR). Results Median macroscopic and microscopic esophagitis scores in groups A' (n=10) and B' (n=8) were 1.0 and 1.5,and 2.0 and 2.5, respectively. There were no significant differences in the macroscopic or microscopic esophagitis scores between the two groups (Z=-0.330, P=0.741; Z=-0.142, P=0.887, respectively). Immunohistochemical staining showed that HSP27 was expressed in all layers of the esophageal epithelia in RE and control rats. FQ-PCR showed that HSP27mRNA levels in the lower esophageal tissue in RE group (groups A' and B') were higher than those in control group (groups C' and D') (Z=-0.249, P=0.001). HSP27 mRNA expression in the lower esophageal tissue was significantly different in groups B' and D' (Z=-3.027, P=0.002). And the levels of HSP27 mRNA expression in severe RE group (microscopic esophagitis score: 3) were higher than in mild RE group (microscopic esophagitis score: 1-2) and control group (Z=-3.396, P=0.001; Z=-3.855, P