AIM: To investigate the optimal height of anastomotic in endoscopic dacryocystorhinostomy.METHODS: This was a prospective randomized controlled study. Totally 229 patients(255 eyes)who were treated with endoscopic dacryocystostomy in Hankou Eye Hospital of Wuhan Aier from January 2019 to August 2020 were selected as the research objects. Including three types of patients: acute dacryocystitis, chronic dacryocystitis and nasolacrimal duct obstruction. Each type of patients were randomly divided into four groups: A, B, C and D. The No.7 lacrimal passage probe was inserted from the upper lacrimal puncta into the bone hole of lacrimal passage stoma. The probe head was close to the upper end of the bone hole, and the angle between the probe and the horizontal line of inner and outer canthus was measured α. Group A α1: -15°to +15°; Group B α2: +16°to +30°; Group C α3: +31°to +45°; Group D α4: +46°to +75°. All patients were followed up to 3mo postoperative. The amount of intraoperative blood loss, operation time and postoperative efficacy were recorded.RESULTS: At 3mo postoperative, the intraoperative blood loss in Group A was more than that in Groups B, C and D, and the operation time was the longest. The operation time of Group D was shorter than that of Groups A, B and C(all P<0.05), but there was no significant difference between Groups B and C(P>0.05). The curative effect of Group B was the best and the Group D was the worst(all P<0.05), and there was no significant difference between Group A and Group C(P>0.05).CONCLUSION: The probe angle from +16°to +30°was the optimal height of anastomotic in endoscopic dacryocystorhinostomy.