Objective:To evaluate the effect of electroacupuncture preconditioning on cellular immune function in the patients undergoing thyroid surgery.Methods:Sixty-six patients of either sex, aged 30-55 yr, with body mass index of 18.5-23.9 kg/m 2, of American Society of Anesthesiologists Physical Status classification ⅠorⅡ, were selected and divided into electroacupuncture preconditioning group (group D) and control group (group C) by a random number table method, with 33 cases in each group. Patients in both groups received combined intravenous-inhalational anesthesia. Before anesthesia induction, both Hegu and Neiguan acupoints were stimulated for 30 min using a continuous wave at a frequency of 2/100 Hz, and the stimulation intensity was subjected to patient tolerance in group D. Group C received sham electroacupuncture for 30 min without stimulation. Venous blood samples were collected at 30 min before anesthesia induction (T 0) and 12, 24 and 48 h after anesthesia (T 1-3). The percentages of T lymphocyte subsets (CD3 +, CD4 +, CD8 +, CD4 + /CD8 + ) and natural killer cells and concentrations of interleukin-6 and tumor necrosis factor-alpha in the serum were measured by flow cytometry. Results:Compared with group C, the percentage of CD3 +, CD4 + and natural killer cells and ratio of CD4 + /CD8 + were significantly increased at T 1, 2, and the concentrations of interleukin-6 and tumor necrosis factor-alpha in the serum were decreased at T 1-3 in group D ( P<0.05). Conclusions:Electroacupuncture preconditioning can improve cellular immune function in the patients undergoing thyroid surgery.