Abstract: Objective To observe the effect of different concentrations of dexmedetomidine on of stress reaction in elderly patients undergoing pulmonary lobectomy. Methods Sixty cases of elderly patients needed pulmonary lobectomy were selected as the research objects,according to the matching grouping method they were divided into three groups with each group of 20 cases.Before inducting give different concentrations of dexmedetomidine infusion.The group A,B,and C were adopted 0.4 μg/kg,0.6 μg/kg,and 0.8 μg/kg,respectively,while pump injection for 10 min.All patients were given penehyclidine,propofol,fentanyl,cisatracurium for induction.Adopted double cavity intubation give propofol,remifentanil,cisatracurium for maintain depth of anesthesia,and maintain the BIS around 40-60,to compare hemodynamic indexes among three groups of patients at different time,and determine cortisol concentrations to assess stress reaction. Results After intubation,after placing lateral decubitus position,intraoperative 1 h and pull tube immediately,the heart rate and mean arterial pressure in group A were higher than those in group B,group C and group B was higher than those in group C,group B’ blood pressure and heart rate were more stable,all P＜0.05.The concentrations of cortisol in A group were higher than those in B and group,C group,and P＜0.05.After intubation,lateral position,skin incision,intraoperative 1 h,operation at the end and pull tube immediate cortisol concentrations were higher than that in group C,P＜0.05. Conclusion Hemodynamics after infusion of 0.6 μg/kg dexmedetomidine in patients undergoing lobectomy is more stable,and it can effective intraoperative stress response,so it has important clinical value.