Objective: To observe the effect of Pinelliae Rhizoma Praeparatum Cum Alumine polysaccharides(PRPCAP)on airway mucus secretion in rats with allergic asthma, in order to study the material basis of the "macromolecule" component of the polysaccharides as the original medicinal materials. Method: The 60 SPF-grade Wistar rats were induced by intraperitoneal injection of chicken ovalbumin (OVA) and aluminum-magnesium adjuvant, except for the normal control group. The OVA solution was aerosolized to establish a rat model of allergic asthma. After successful modeling, the rats were randomly divided into 5 groups, namely allergic asthma model group, positive drug group (montalurast sodium,5 mg·kg^-1), high-dose PRPCAP group (400 mg·kg^-1), middle-dose PRPCAP group (200 mg·kg^-1) and low-dose PRPCAP group (100 mg·kg^-1). The contents of interleukin-4 (IL-4) and interferon-γ (IFN-γ) in serum and bronchoalveolar lavage fluid (BALF) supernatant were determined by enzyme-linked immunosorbent assay (ELISA), and the count of eosinophils (EOS) was detected by BALF sediment. The histopathological changes were observed by hematoxylin-eosin (HE) staining in lung tissue. The mRNA expression of mucin 5AC (MUC5AC) was detected by Real-time fluorescent quantitative polymerase chain reaction (Real-time PCR). Result: Compared with the normal control group, serum IL-4 level in the allergic asthma model group was significantly increased (P<0.01), IFN-γ level was significantly decreased (P<0.01), and EOS counts in BALF were significantly increased (P<0.01). Compared with the allergic asthma model group, the positive drug group, and high, middle, and low-dose PRPCAP groups could significantly reduce the serum IL-4 content (P<0.01), while high and middle-dose PRPCAP groups could significantly reduce the content of IL-4 in BALF (P<0.05, P<0.01), the middle-dose PRPCAP group could significantly increase the content of IFN-γ in serum (P<0.05), EOS counts in BALF were significantly lower in the positive drug group and all of PRPCAP groups (P<0.01). HE staining showed the pathological changes in the lung tissue of the allergic asthma model group and a mitigating effect in the positive drug group and all of PRPCAP groups. Compared with the normal control group, the expression of MUC5AC mRNA in the lung tissue of rats with allergic asthma was significantly increased (P<0.01). Compared with the model group of allergic asthma rats, the positive drug group and all of PRPCAP groups showed significant decrease in MUC5AC mRNA (P<0.01). Conclusion: The "macromolecule" component of polysaccharides in the Pinelliae Rhizoma Praeparatum Cum Alumine may be the material basis for the efficacy of eliminating dampness and eliminating phlegm.