Objective To explore the role of Erianin in atopic dermatitis (AD) and its regulatory mechanism involving the high-mobility group box 1 (HMGB1)/receptor for advanced glycation end products (RAGE)-Ras homolog gene family member A (RhoA)/Rho-associated protein kinase 1 (ROCK1) signaling pathway. Methods An AD model was induced in BALB/c mice using 1-chloro-2,4-dinitrobenzene (DNCB). Skin thickness and spleen and lymph node weight were measured and pathological changes in the back skin and ears were detected using methylamine blue and hematoxylin and eosin staining. Inflammatory factors were detected by enzyme linked immunosorbent assay. An in vitro model of AD was established in HaCaT cells stimulated by tumor necrosis factor (TNF)-α. Cellular reactive oxygen species (ROS) were detected by flow cytometry and mitochondrial ROS (mtROS) were detected by immunofluorescence assay. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling. HMGB1, RAGE, RhoA, and ROCK1 proteins were detected by Western blot. Results Erianin inhibited the increase in skin thickness, reduced the spleen and lymph node weights, improved the infiltration of inflammatory cells and the degranulation of mast cells, and reduced the levels of inflammatory factors(P<0.05). Erianin also reduced the production of cellular ROS and mtROS induced by TNF-α in vitro(P<0.01), and decreased the protein expression of HMGB1, RAGE, RhoA, and ROCK1(P<0.01). Treatment of HMGB1stimulated HaCaT cells with a RAGE-specific blocker (TFA) had no effect on HMGB1 expression, while expression levels of RAGE, RhoA, and ROCK1 were decreased(P<0.01). Cells treated with the Rho kinase inhibitor Y-27632 +r-HMGB1 group showed similar result to the TFA+r-HMGB1 group, except for RAGE. Conclusions Erianin relieves AD by regulating the HMGB1/RAGE-RhoA/ROCK signaling pathway.