Objective: To study the effect of μ-opioid receptor (MOR) expression in the inflammatory skin tissue and the effect of electroacupuncture (EA) onthe topical immunoreaction (IR) of MOR positive fibers in adjuvant arthritic (AA) rats. Methods: A total of 48 SD rats were randomized into control (n =8), model (n= 10), focus-side-EA (n = 10), non-acupoint-EA (n = 10), and healthy-side-EA (n = 10) groups. AA model was established by subcutaneous injection of complete Freunds adjuvant (CFA, 50 μL) into the left hind paw.EA (4-16 Hz, 0.5-1.5 V) was applied to "Huantiao" (环跳 GB 30) and "Yanglingquan" (阳陵泉 GB 34)on the focus or healthy side and non-acupoints for 30 min. Non-acupoints used were the two sites 5 mm to GB 30 and GB 34 on the healthy side. The topical MOR IR-positive fibers in the dermal and subcutaneous tissues of the focus was stained with immunohistochemical method. The severity of pain was detected by foot (anklejoint)-bending test. Results: Compared with model group, the "foot-bending test" score decreased significantly in focus-side-EA group on the 9th and 11th day (P＜0.05) and in non-acupoint-EA group on the 8th, 9th and 11thd after injection of CFA (P ＜0.05), indicating that EA of bilateral GB 30 and GB 34 and non-acupoints all can relieve pain. From the 13th day on, no significant differences were found in "foot-bending test"scores among the 3 EA groups and model group (P＞0.05). In comparison with control group, the area values of MOR IR-positive nerve fibers in the focus tissue were significantly higher in 3 EA groups (P＜0.05).The area values of MOR IR-positive nerve fibers in the focus in model group and 3 EA groups were significant higher than that in control group (P＜0.05). Compared with model group, the area values of MOR IR-positive fibers in focus-side-EA group and healthy-side-EA group increased significantly ( P ＜0.05); while those of MOR IR-positive fibers in non-acupoint-EA group and healthy-side-EA group were significantly lower than that in focus-side-EA group ( P ＜0.05), and no significant differences were found among model group,healthy-side-EA group and non-acupoint-EA group in the area of MOR IR-positive fibers (P＞0.05), indicating a stronger effect of EA of acupoints on the focus side. Conclusion: EA of GB 30 and GB 34 can relieve inflammatory pain and up-regulate the expression of MOR IR-positive fibers in the focal skin tissues in AA rats,exerting anti-inflammatory and analgesic effects.