Abstract: To explore the optimal extraction process and rheological properties of crude polysaccharides from common lopatherum herb and evaluate their immunological activity. In this experiment, common lopatherum herb was used as raw materials. The optimal extraction process conditions for the crude polysaccharides from common lopatherum herb were optimized by combining single-factor experiments with the response surface methodology, and the monosaccharide composition was detected by ion chromatography. Moreover, the rheological properties of the crude polysaccharides from common lopatherum herb were determined using a Malvern Kinexus Pro+rheometer. The effect of the crude polysaccharides from common lopatherum herb on the proliferation activity of RAW 264.7 mouse macrophages was detected by the CCK-8 method, and their immunomodulatory activity was evaluated based on the expression levels of TNF-α, IL-6, and NO. The optimal extraction conditions were determined as follows: extraction time of 92 min, extraction temperature of 67 ℃, alkali concentration of 0.04 mol/L, and solid-liquid ratio of 1:28 g/mL. Under these conditions, the yield of crude polysaccharides from common lopatherum herb was the highest, reaching 3.21%±0.17%. The total sugar content of crude polysaccharide from common lopatherum herb was determined to be 54.7%±0.7% by the phenol-sulfuric acid method. The monosaccharide composition mainly consisted of fucose, arabinose, rhamnose, galactose, glucose, xylose, mannose, galacturonic acid, and glucuronic acid, with a molar percentage of 0.81:7.53:21.45:20.70:30.61:3.50:3.05:9.52:2.84. The steady shear test results indicated that the crude polysaccharide solution of common lopatherum herb was a pseudoplastic fluid with shear thinning characteristics. The dynamic shear test results showed that the presence of high frequency could enhance the gel property of the crude polysaccharide solution of common lopatherum herb. The crude polysaccharides extracted from common lopatherum herb had no significant effect on the proliferation activity of RAW 264.7 mouse macrophages. However, within the concentration range of 50~400 μg/mL, the crude polysaccharide solution from common lopatherum herb could moderately promote the secretion of TNF-α, IL-6, and NO by RAW 264.7 mouse macrophages. The research results can provide a theoretical basis for the development and application of crude polysaccharides from common lopatherum herb in the fields of food and medicine.