Objective: To investigate the effect of intranasal administration of dexmedetomidine on improving postoperative cognitive function in elderly patients. Methods: A total of 120 elderly patients who underwent thoracoscopic lobectomy under general anesthesia in Drum Tower Hospital Affiliated to Nanjing University School of Medicine from October 2019 to October 2021 were selected. Fifty-eight patients with non-sleep disorder were included in the control group and randomly divided into a control group A and a control group B, each group with 29 cases. Patients in the control group A ware sprayed with 0.02 mL/kg normal saline through the nose 30 min before the end of the operation, and patients in the control group B were sprayed with 2 μg/kg dexmedetomidine through the nose 30 min before the end of the operation. Sixty-two patients with disabilities were included in the study group and randomly divided into a study group A and a study group B, each group with 31 cases. Patients in the study group A were sprayed with 0.02 mL/kg normal saline through the nose 30 min before the end of the operation, and patients in the study group B were sprayed with 2 μg/kg dexmedetomidin through the nose 30 min before the end of the operation. The postoperative recovery quality, pain degree, cognitive function changes, and the incidence of complications after extubation were compared in the 4 groups. Results: The score of postoperative recovery quality in the control group B was higher than that in the control group A (P<0.05); the score of postoperative recovery quality in the study group B was higher than that in the study group A (P<0.05); the score of postoperative recovery quality in the control group A was higher than that in the study group A (P<0.05). The Visual Analogue Scale (VAS) scores at the moment of extubation and at 4, 8, 12, and 24 h after the extubation in the study group A were higher than those in the control group A, the control group B, and the study group B (all P<0.05). The Mini-Mental State Examination (MMSE) score of the study group A was lower than that of the control group A, the control group B, and the study group B on the 1st day after the operation (P<0.05); there was no significant difference in MMSE scores between the study group B and the control group B on the 1st day after the operation (P>0.05). The incidence of total complications after extubation in the study group B was lower than that in the study group A (P<0.05); there was no significant difference in the incidence of complications after the extubation between the study group B and the control group B (P>0.05). Conclusion: The elderly patients with sleep disorders have poor postoperative recovery quality, severe pain, and large postoperative cognitive function reduction after the operation. Nasal administration of dexmedetomidine can significantly improve the quality of postoperative recovery, relieve the degree of pain, reduce the degree of postoperative cognitive dysfunction, and reduce the incidence of complications after extubation.