Objective To investigate the effect of transcutaneous auricular vagus nerve stimulation (taVNS) on preoperative anxiety and sleep quality of patients with thyroid surgery. Methods Eighty eight patients undergoing thyroid surgery were enrolled as research objects. According to the random number table method, the patients were assigned into taVNS group (group T) and sham stimulation group (group S) (n=44). TaVNS was given to patients in group T for 30 min one night before operation, the current intensity is the maximum extent that the patient can tolerate. In group S, a vagus nerve stimulator was placed in the same auricular region and the stimulation parameters were set as same as those in group T. Record the Trait Anxiety Inventory (TAI) scores before intervention (T0), the State Anxiety Inventory (SAI) scores, SAI score difference (dSAI=SAIT0－SAIT1), Amsterdam Preoperative Anxiety Scale (APAISa) scores, and hemodynamic [mean arterial pressure (MAP). The heart rate, the pulse oxygen saturation (SpO2)] conditions were also recorded at T0 and after intervention (T1). Athens Insomnia Scale (AIS) scores were recorded at T0 and the next morning (T2). The extent of anxiety, the sleep quality, and correlations of these scores with sleep quality were compared between the two groups. The occurrence of adverse reactions during the study period was also recorded between the two groups. Results Compared with T0, SAI scores, APAISa scores, the MAP, and heart rates of patients in both groups decreased at T1 (all P<0.05); AIS scores of patients in both groups decreased at T2 (all P<0.05). Compared with group S, the dSAI of group T were higher (P<0.05); the SAI scores, APAISa scores, the proportion of patients with moderate and severe anxiety of group T decreased at T1 (P<0.05), the proportion of patients with mild anxiety in group T increased at T1 (P<0.05); At T2, AIS scores and the incidence of insomnia in group T decreased (all P<0.05), while the incidence of insomnia without sleep disturbance and suspected insomnia increased (all P<0.05). At T0, AIS scores were positively correlated with TAI scores (r=0.33, P<0.05). At T0 and T1, AIS scores were positively correlated with SAI scores (T0: r=0.37，P<0.05; T1: r=0.44, P<0.05) and APAISa scores (T0: r=0.37, P<0.05; T1: r=0.37, P<0.05). No adverse reaction occurred in both groups. There was no significant difference in other indexes between the two groups (all P>0.05). Conclusions Transcutaneous auricular vagus nerve stimulation can significantly reduce the severity of preoperative anxiety and the incidence of sleep disorder in patients undergoing thyroid surgery.