Objective To analyze the prefrontal electroencephalogram characteristics of patients with emergence delirium(ED)after hip or knee arthroplasty.Methods Sixty-four patients undergoing elective hip or knee arthroplasty were selected,12 males and 52 females,aged≥60 years,BMI 18.5-30.0 kg/m2,ASA physical status Ⅱ or Ⅲ.The confusion assessment method-intensive care unit(CAM-ICU)and the Richmond agitation-sedation scale(RASS)were used to determine the occurrence of ED dur-ing postoperative anesthesia.The patients were divided into two groups according to whether delirium oc-curred during emergence from anesthesia:the emergence delirium group(ED group)and the non-emergence delirium group(non-ED group).The patients'raw EEG data during the emergence phase were recorded by the EEG monitor,and the data from before(5-10 minutes after discontinuation of the drug)and after emergence(15-20 minutes after removal of the laryngeal mask)were intercepted and spectrally analyzed.Results Twenty-eight patients(44％)developed ED.EEG changes during emergence from anes-thesia were consistent in both groups:the spectral edge frequency(SEF)was increased,the β and y wave power was increased,and the peak α wave frequency was decreased.Compared with the pre-emergence state,the θ and α wave power were significantly lower and the peak α wave power was significantly lower in the non-ED group during full awakening(P＜0.05),and the difference between the α wave power and the peak α wave power was not statistically significant in the ED group during full awakening.Sample entropy and alignment entropy of patients in the ED group before emergence and in full awakening were significantly higher than those in the non-ED group(P＜0.05).Conclusion The θ wave power,α wave power,and peak α wave power were significantly lower during emergence from anaesthesia in patients with no delirium.In patients who developed ED,there was no significant change in α wave power or peak α wave power dur-ing emergence from anesthesia,but there was an increase in sample entropy and alignment entropy.