Abstract: Objective To observe the effect of long-term exposure to strong electromagnetic environment on the cytokine level in blood of the workers. Methods Men who had engaged in work associated with electromagnetic radiation for at least one year were consecutively recruited as exposed group,while males in the same department without exposure to strong electromagnetic radiation as non-exposed group.First,multi-point monitoring of the electromagnetic strength of the working environment were done,and then 7 kinds of cytokines from whole blood plasma from peripheral vein of all recruited candidates,including interleukin-1β (IL-1β),interleukin-6 (IL-6),interleukin-7 (IL-7),interleukin-8 (IL-8),interleukin-10 (IL-10),tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) were detected and evaluated,of which the change trend over time were analyzed. Results No significant difference was found in age,gender,work experience and body mass index (BMI) between the exposed group (n=239) and the non-exposed group (n=203).Compared with the non-exposed group,the levels of IL-1β (24.09±3.77pg/ml vs 24.89±3.97pg/ml,P=0.030),IL-6 (15.74±2.26pg/ml vs 16.46±2.49pg/ml,P=0.001) and IL-8 (13.28±4.02pg/ml vs 14.10±3.73pg/ml,P=0.026) in the exposed group significantly reduced.The levels of IL-1β,IL-6 and IL-8 in the exposed group showed greater fluctuation than those in the non-exposed group over years of exposure.The level of IL-8 in the exposed group was correlated to the years of exposure and age,respectively.No significant difference was observed in IL-7,IL-10,TNF-α and IFN-γ between the two groups (P>0.05). Conclusion Long-term exposure to strong electromagnetic environment can reduce the level of cytokines in blood of the workers,which may affect the body's immune defense function.