Objective To investigate the effect of continuous intravesical installation of sodium hyaluronate combined with hyperbaric oxygen therapy on radiation-induced hemorrhagic cystitis.Methods A total of 40 patients suffering from hemorrhagic cystitis after receiving radiotherapy for pelvic malignant tumors and visiting our hospital from January 2015 to January 2019 were randomly divided into combination group treated with continuous intravesical installation of sodium hyaluronate combined with hyperbaric oxygen therapy and hyperbaric oxygen group treated with hyperbaric oxygen therapy alone. The hematuria, urination frequency, and the score of hematuria colorimetric card (1 to 10) were evaluated 6 months prior to the treatment, and 6, 12 and 18 months after the treatment.Results There was no significant difference in the complete remission rate and partial remission rate between the two groups at 6, 12 and 18 months after the treatment (P > 0.05). The urination frequency and the score of hematuria colorimetric card were different between the two groups and among different time points after the treatment (P < 0.05). The urination frequency and the score of hematuria colorimetric card were lower in the combination group, which was suggestive of a better effect of the combined treatment (P < 0.05). There was no difference in the change trend of urination frequency between the two groups (P > 0.05), but the change trend of the score of hematuria colorimetric card was different between the two groups (P < 0.05). At 6 months after the treatment, the incidence of side effects in the combination group was higher than that of the hyperbaric oxygen group (P < 0.05). However, there was no significant difference in the incidence of side effects between the two groups at 12 and 18 months after the treatment (P > 0.05).Conclusions The continuous intravesical installation of sodium hyaluronate combined with hyperbaric oxygen therapy is well tolerated for the treatment of radiation-induced hemorrhagic cystitis. It can continuously reduce bladder bleeding, severity of hematuria and urination frequency for at least 12 months.