Objective:To explore the treatment efficacy of neuroendoscope-assisted exploration and release of the outflow tract of the fourth ventricle in patients with Chiari malformation type I.Methods:Ninety-five patients with Chiari malformation type I, admitted to our hospital from January 2016 to January 2020, were chosen in our study. Patients from observation group ( n=57) were treated with posterior cranial fossa decompression+subdural tonsillectomy+endoscope-assisted exploration and release of the outflow tract of the fourth ventricle+enlarged reconstruction of the occipital cistern. Patients from control group ( n=38) were treated with posterior fossa decompression+subdural tonsillectomy+enlarged reconstruction of the occipital cistern. All patients were followed up for one year. Data of surgical duration, intraoperative blood loss, postoperative length of hospital stay, and incidence of complications were retrospectively analyzed in patients from the two groups, and the imaging changes of spinal cavity were observed before surgery and during postoperative follow-up. Chicago Chiari Outcome Scale (CCOS) was used to evaluate the prognoses of all patients (scores of 11-16 were defined as good prognosis). The differences of good prognosis rate among patients with different gender, age, degrees of tonsillar herniation and distributions of spinal cavity segments were analyzed. Results:There was no significant difference in surgical duration, intraoperative blood loss, postoperative length of hospital stay or incidence of complications between the two groups ( P>0.05). As compared with the control group (65.5%), the observation group had higher syringomyelia minification (75.5%) during postoperative follow-up, without significant difference ( P>0.05). The good prognosis rate of the observation group during postoperative follow-up (91.2%) was significantly higher than that of the control group (78.9%, P<0.05). Female patients, patients with age≤45 years, and patients with tonsillar herniation level below the atlas had significantly higher good prognosis rate than male patients, patients with age>45 years, and patients with tonsillar herniation level between the foramen magnum and the atlas during postoperative follow-up, respectively ( P<0.05). Conclusion:As compared with conventional surgery, neuroendoscope-assisted exploration and release of the outflow tract of the fourth ventricle is more effective in patients with Chiari malformation type I, and the good prognosis rate is likely higher in female patients, patients with age≤45 years, and patients with tonsillar herniation level below the atlas.