AIM: To study the effect of achyranthes bidentata polysaccharides(ABPS) on the expression of signal transducer and activator of transcription 6 and its mRNA in bronchus of a rat model of asthma. METHODS: Thirty male SD rats were randomly divided into three groups: the control group, asthma group and ABPS group. The total cell numbers, eosinophils (EOS) numbers and differentiated cell numbers in bronchoalveolar lavage fluid (BALF) were counted by different count fluids. The concentrations of IL-4 in serum and BALF were measured by sandwich ELISA. The protein expressions of STAT6 were detected by immunohistochemistry techniques. The mRNA expressions of STAT6 were detected by hybridization in situ. RESULTS: (1) The total cell numbers in BALF, the absolute numbers of EOS, the ratios of eosinophils to the total cell numbers (EOS%) of asthma group were all significantly higher than those of the control group (P < 0.01). The total cell numbers in BALF, the absolute numbers of EOS and EOS% of ABPS group were all significantly lower than those of asthma group (P < 0.01). (2) The concentrations of IL-4 in BALF and serum of asthma group were significantly higher than those of control group (P < 0.01), while the concentrations of IL-4 in BALF and serum of ABPS group were significantly lower than those of asthma group. (3) Immunohistochemistry showed that the protein content of STAT6 around the bronchus of asthma group was significantly higher than that of the control group (P < 0.01), while that of ABPS group was significantly lower than that of asthma group , the epithelial cells were the chief expression cells; hybridization in situ showed that the mRNA expression of STAT6 around the bronchus of asthma group was significantly higher than that of the control group (P < 0.01), while that of ABPS group was significantly lower than that of asthma group , the epithelial cells were the chief expression cells. CONCLUSION: STAT6 protein and STAT6 mRNA were found strongly expressed in rat asthma model, the epithelial cells were the chief expression cells. ABPS had an inhibitory effect on airway inflammation cells infiltration such as EOS, it significantly depressed STAT6 and its mRNA expression, thus reduced the synthesis of IL-4 might be key in modulating mechanism of asthma.