【Abstract】 Objective To analyze the effect of dexmedetomidine (DEX) on serum inflammatory factor expression and stress response in patients with lung cancer undergoing radical mastectomy. Methods The clinical data of 94 patients undergoing elective lung cancer radical surgery admitted to our hospital from July 2015 to June 2017 were prospectively analyzed. The selected patients were divided into study group (n=47 cases) and control group (n=47 cases), according to different treatment methods. Patients in the study group were intravenously infused with DEX 1ug/kg 10 minutes after endotracheal intubation, and then continued at an infusion rate of 05ug/kg·h until 30 minutes before the end of surgery. The control group received the same dose of normal saline, the changes of inflammatory factors and stress response indicators at different time points in the two groups were observed. Results At the time of T1 and T2, the levels of serum E, NE and COR in the two groups were significantly higher than those in T0 (P＜005). The serum E, NE and COR levels in the study group were significantly lower than those in the control group ( P＜005). At the time of T1 and T2, serum IL6, TNFα and hsCRP levels in the two groups were significantly higher than those in T0 (P＜005). The serum IL6, TNFα, hsCRP in the study group were significantly lower than those in the control group (P＜005). There was no significant difference in single lung ventilation time, intraoperative blood loss, fluid volume and 24h urine volume between the two groups (P＞005). The postoperative recovery time and extubation time of the study group were significantly lower than those of the control group, and the Ramsay sedation score of the study group was significantly higher than that of the control group (P＜005). Conclusion DEX in patients undergoing radical mastectomy can effectively reduce the secretion of inflammatory factors during singlelung ventilation, inhibit the inflammatory response, and effectively reduce the level of intraoperative stress response, improve the effect of anesthesia and surgical treatment, improve the quality of postoperative recovery, and have positive significance for promoting rapid recovery of patients' diseases.