Abstract: Objective: To investigate the effects of dexmedetomidine(DEX) on preoperative oxidative stress caused by laparoscopic cholecystectomy. Methods: Eighty patients scheduled for laparoscopic cholecystectomy in our hospital from Mar. 2012 to Jun. 2013 were randomly divided into the DEX group(D group) and control group(C group)(40 cases each group). The D and C groups were intravenously and continuously infused using DEX and isovolume normal saline after anesthesia induction. The serum levels of MDA, SOD and ROS in two groups before operation(T₀), at the moment of opening pneumoperitoneum(T₁), at the end of operation(T₂) and after 24 h of operation(T₃) were measured. Results: The differences of the preoperative blood pressure and heart rate change between two groups were not statistical significance(P>0.05). Compared with T₀, the serum levels of MDA and ROS, and level of SOD at T₁, T₂, T₃ in two groups were singificantly higher and lower, respectively(P<0.01). The levels of MDA, SOD and ROS at T₁, T₂ and T₃ in D group were significantly lower than those in C group(P<0.01). Conclusions: Continuously intravenous injection of dexmedetomidine can effectively alleviate the preoperative oxidative stress caused by laparoscopic cholecystectomy.