Abstract: Objective: In this study, the response surface method (RSM) was used to optimize the extraction conditions of Glehniae Radix polysaccharides (GLP) by cellulase and ultrasonic-assisted, and its physicochemical properties and immunomodulatory activity were studied. Methods: The factors of enzymolysis time, material to liquid ratio, ultrasonic time, ultrasonic temperature and cellulase additions were selected as influencing factors, the yield of GLP was the evaluation index, and single factor experiments was conducted. Based on single factor results, the optimal extraction process of GLP was obtained by RSM. The physicochemical properties were analyzed by scanning electron microscope (SEM), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), fourier transform infrared spectroscopy (FT-IR), and high performance liquid chromatography (HPLC), and the immunomodulatory activity of RAW 264.7 macrophage was evaluated by in vitro test. Results: The optimal conditions were as follows: Enzymolysis time was 112 min, material to liquid ratio was 1:30 g·mL⁻¹, ultrasonic time was 41 min, ultrasonic temperature was 65 ℃, and cellulase additions was 2%. Under these conditions, the yield of GLP was 39.58%±0.90%. Besides, GLP was mainly composed of glucose, well thermal stability. The results of in vitro immunomodulatory activity showed that GLP could significantly (P<0.05) promote the proliferation of RAW 264.7 macrophages in the concentration range of 0.5 to 250 μg·mL⁻¹, and significantly (P<0.05) inhibit LPS induced overactivation of macrophages in the concentration range of 0.5 to 10 μg·mL⁻¹. Conclusions: This process was stable and feasible, which not only had a relatively high GLP yield, but also had certain immunoregulatory activity.