Objective:To study the effect of dexmedetomidine (DEX) on the post operative cognitive dysfunction (POCD) of elderly patients with esophageal cancer using one-lung ventilation (OLV). Methods:60 cases of esophageal cancer radical (ASA Ⅰ~Ⅱ) in elderly patients with esophageal cancer were chosen, from June 2015 to February 2016 in our hospital line. These patients were divided into two groups by random number method. These patients in the test group (n=30) were induced using DEX 1.0 μg·kg^-1, and the injection were completed in 10 min. After induction, they received the DEX 0.6 μg·kg^-1·h^-1 until the end of the operation. These patients in the control group(n=30) received the normal volume of saline. Systemic anesthesia was used in all cases, and bilateral endotracheal intubation was performed. At 2 h before surgery and 4 d after surgery, the status of cognitive function using Mini-mental Status Examination (MMSE) was evaluated; before the induction (T₀), OLV for 30 min (T₁), at the end of the operation (T₂), 24 h after surgery (T₃), determination of brain function indexes were evaluated, including the neuron-specific enolase (NSE), nervous system specific protein (S-100β), and the inflammatory cytokines interleukin 6 and tumor necrosis factor α (TNF-α) were evaluated.Results:There was no statistically significant difference between the two groups, such as sex, age, weight, operation time, proportion of patients with hypertension or cerebrovascular disease, OLV time, infusion volume, blood loss (P > 0.05). There were 3 POCD cases at 4 d after surgery in the test group, rate of 10%, while there were 8 POCD cases (4 cases mild, 2 cases moderate, 2 cases severe) in the control group, rate of 26.7%, the difference of POCD incidence between two groups was statistically significant (P<0.05). Compared with before the surgery, in the test group, the difference of the MMSE scale score at 4 d after surgery was not statistically significant (P>0.05), but in the control group, the difference was statistically significant (P<0.05). The difference of the MMSE scale score at 4 d after surgery between the two groups was statistically significant (P<0.05). Compared with T₀, NSE and S-100β oftwo groups at T₁, T₂ and T₃ were significantly higher (P<0.05), but compared with the control group, the NSE and S-100β of test group were significantly lower (P<0.05). Compared with T₀, the IL-6, TNF-α of two groups at T₁, T₂ and T₃ were significantly higher (P<0.05); but compared with the control group, at T₂ and T₃, the IL-6, TNF-α of test group were significantly lower (P<0.05). Conclusion:DEX can significantly improve cognitive function after surgery for elderly patients with esophageal cancer using OLV, reduce the incidence of POCD, lower the levels of serum NSE, S-100β, IL-6, TNF-α.