Objective,2,To investigate the effect of self-designed formula Longmu Decoction on the methylation level of high-affinity IgE receptor （FcERI） γ subunit promoter and Th2 immune response in mice with atopic dermatitis （AD）.,Methods,2,Animal grouping and modeling：30 BALB/C mice were divided into model group，traditional Chinese medicine group and blank group，with 10 mice in each group. Among them，20 mice in model group and traditional Chinese medicine group were used to make AD model. Traditional Chinese medicine group was given Longmu Decoction by intragastric administration，and the model group and the blank group were given 0.9% normal saline by intragastric administration. All mice were given intragastric administration once a day for 3 weeks. First，the mice in each group were routinely sacrificed by cervical dislocation，femur and tibia of them were obtained，and bone marrow dendritic cells （BMDC）were isolated and cultured；then，the blood of Chinese medicine group and model group mice were immediately collected through the abdominal aorta，the serum was separated，and 10% serum containing Longmu decoction and 10% non-medicated serum were prepared respectively. BMDC was randomly divided into the control group and medicine group. The control group was added with 10% non-medicated serum and the medicine group was added with 10% serum containing Longmu Decoction both continuously cultured for 48 hours.CD11c positive rate of BMDC was detected by flow cytometry. The expression of FCER1γ protein in BMDC cells was detected by Western blotting. Methylation specific PCR （MSP） detection； the levels of McP-1 and IL-12 in the supernatant of BMDC cells were determined by ELISA. The double positive rate of CD4 and IL-4 in BMDC was detected by flow cytometry.,Results,2,Compared with the control group，the expression of FCER1γ protein in BMDC was lower in Chinese medicine group（,P,<,0.05），and the methylation level of FCER1γ subunit promoter in the drug-containing serum group was higher than that in the control group（,P,<,0.05）. Compared with control group，the level of MPC-1 was lower and the level of IL-12 was higher in Chines medicine group（,P,<,0.05）. Compared with blank group，there was no significant difference in CD4 and IL-4 double positive rates in Chines medicine group（,P,>,0.05）.,Conclusion,2,Longmu Decoction can increase the methylation level of FcER Iγsubunit gene regulatory sequence in dendritic cells of AD mice，and further inhibit the overexpression of FcERIγ subunit and FcERI on cell surface，promote Th1 differentiation and inhibit Th2 immune response.