Objective:To reveal the mechanism of Mahuang Lianqiao Chixiaodou decoction and its disassembled formula for improving the skin barrier function in a mouse model of atopic dermatitis (AD).Methods:Sixty specific-pathogen free male BALB/c mice were randomly divided into the control group,model group,whole formula group (WF),exterior-releasing formula group (ERF),interior-clearing for-mula group (ICF),and positive control group (PC).A mouse model of AD was established using the semi-antigen 2,4-dinitrofluorobenzene induction method.The lesion scores,transepidermal water loss and pH,and skin histopathology of mice in each group were observed.The expressions of filaggrin,loricrin,and involucrin were detected by the streptavidin peroxidase immunohistochemical method and western blotting,and their mRNA expressions were detected by quantitative polymerase chain reaction.Results:Mice in the WF,ERF,ICF,and PC groups showed reduced skin lesion performance,improved histopathology,decreased skin lesion score,transepidermal water loss and pH,and upregulated ex-pressions of proteins including filaggrin,loricrin,and involucrin,and their mRNAs.The most obvious regulatory effect was observed in the WF group,followed by the ICF,ERF,and PC groups,accordingly.Conclusions:Mahuang Lianqiao Chixiaodou decoction and its disassembled formula can improve the skin barrier function in a mouse model of AD by upregulating filaggrin,loricrin,and involucrin,and their mRNA expressions,and the most optimal effect was noted in the WF group,followed by the ICF and ERF groups,which suggests that the effect of clearing heat and resolving dampness in improving the skin barrier function of AD is more obvious and is one of the key treatments for AD.