Objective To explore the possible molecular mechanism of Sangxing Decoction in "promoting production of fluid and moistening dryness". Methods One hundred and ten mice were randomized into the normal temperature and humidity group

the warm dryness model group

the warm dryness negative treatment group

and the low and high dose Sangxing Decoction groups

with 22 mice in each group. Warm dryness mice were modeled by synthetic condition of "temperature-relative humidity-wind". After mice were modeled for 6 days

the low and high dose Sangxing Decoction groups were given Sangxing Decoction 0. 009

or 0. 018 g /（ kg·d） by gavage

respectively

and the normal temperature and humidity group and the warm dryness negative treatment group were given equivalent sterile normal saline by gavage

all once daily for 6 days. Changes of mice’s airway and lung histology in each group were examined. Ultra microstructure of middle lobe of left lung was observed. The expressions of aquaporin 5（ AQP5）mRNA and proteins in lung tissue

and the levels of mucoitin

inorganic phosphorus

neutrophil elastase（ NE）

a1-antitrypsin（ a1-AT）

interleukin 10（ IL-10） and platelet activating factors（ PAF） in bronchoalveolar lavage fluid were detected. Results Compared with the normal temperature and humidity group

there were pathological and ultrastructural damage in trachea and lung tissue of mice in the warm dryness model group. The respiratory membrane thickened. The levels of mucoitin

inorganic phosphorus and IL-10 in bronchoalveolar lavage fluid decreased. PAF increased. The expressions of AQP5 mRNA and proteins decreased（ P < 0. 05 or P < 0. 01）. Compared with the warm dryness model group

mice’s tracheal metaplasia

cilium defect and mucous membrane gland metaplasia in the low dose Sangxing Decoction group were improved. Average thickness of respiratory membrane decreased. The levels of mucoitin

inorganic phosphorus

a1-AT and IL-10 in bronchoalveolar lavage fluid increased; while the levels of NE and PAF decreased. The expressions of AQP5 mRNA and proteins in lung tissue increased（ P < 0. 05 or P < 0. 01）.Conclusion Sangxing Decoction "promoting production of fluid"might relate to increasing the secretion of airway fluid and alveolar surfactant

as well as up-regulating the gene expression of AQP5. "Moistening dryness"might be inhibiting the "cascade"of inflammatory cytokines. Thus airway pathological injury might be improved.