Background: Over the past 10 years, endoscopic endonasal dacryocystorhinostomy (EE-DCR)has a trend to gradually become the mainstream method for the treatment of nasolacrimal duct obstructive diseases , but the failure of EE-DCR is not rare in clinical treatment. Therefore, the study will explore the efficacy of treating patients with EE-DCR failure by endoscopic endonasal common canaliculorhinostomy (EE-CAR), in order to improve the success rate of reoperation in patients with EE-DCR failure. Method: Prospective non-randomized controlled study. Patients with EE-DCR failure caused by lacrimal sac nasal mucosal ostium atresia from April 2018 to January 2021 in Hankou Aier Eye Hospital were enrolled. They were divided into two groups according to the principle of voluntariness before surgery. Group A: underwent EE-CAR. Group B: underwent Endoscopic Endonasal Ostial Openning (EE-OO). The postoperative efficacy and complications of the two groups was compared. Results: 44 patients (48 eyes) were included in the comparative analysis, including 26 eyes in group A and 22 eyes in group B. Followed up at 6 months postoperative, the ostium of 22 eyes in group A remained open and the symptoms of tear overflow disappeared. The success rate of surgery was 84.62% (22/26), and 54.55% (12/22) in group B. There was significant difference between the two groups (P<0.05). Conclusions: EE-CAR is better than conventional ostium opening in the treatment of patients with small lacrimal sac remnant after EE-DCR due to ostium atresia.