Objective:To investigate the expression and clinical significance of TET gene and 5hmC in chronic sinusitis. Methods:Acquiring 20 cases of nasal polyps from chronic sinusitis with polyps（CW）, 20 cases of uncinate process tissues from chronic sinusitis without polyps（CS）, 10 cases of middle turbinate tissues from patients with nasal septum deviated as normal group（N）.The expression of TET gene and 5hmC in chronic sinusitis was measured by immunofluorescence, Western-Blot and Quantitative real-time PCR. Results:Both TET1/2/3 gene and 5 hmC were highly expressed in the CS group, but were lower in the CW group and the N group.There were statistically significant differences between the CS group and the CW group（P<0.05）, and between the CS group and the N group（P<0.05）.The expressions of TET1 and TET3 in the N group were higher than those in the CW group, and the difference was statistically significant（P<0.05）. Conclusion:DNA demethylation plays an important role in the formation of nasal polyps.High expression of TET1, TET2, TET3 and 5hmC May reduce the risk of nasal polyps.Increased DNA demethylation in chronic sinusitis may reduce the risk of nasal polyp formation.When the degree of DNA methylation in chronic sinusitis is high and the degree of DNA demethylation is low, the disease may develop to CRSwNP, and when the degree of DNA methylation is low and the degree of DNA demethylation is high, the disease may develop to CRSsNP.