Abstract: OBJECTIVE To explore the effect of vinegar Bupleuri Radix polysaccharides with different molecular weight on the anti-inflammatory and immunomodulatory activity of Raw264.7 macrophage. METHODS Vinegar Bupleuri Radix polysaccharides with different molecular weight were separated by dialysis bags. MTT assay was used to determine the effect of vinegar Bupleuri Radix polysaccharides with different molecular weight on cell viability of Raw264.7 macrophage; neutral red phagocytosis assay was used to determine the effect of polysaccharides on cell phagocytosis; Griess method was used to detect their effect on the release of NO of Raw264.7 inflammatory cell model stimulated by LPS. RESULTS Six different molecular weight of vinegar Bupleuri Radix polysaccharides(<3.5, 3.5-50, 50-100, 100-300, 300-1 000, >1 000 kDa) were separated, and they had no cell toxicity to Raw264.7 macrophage in the range of 1.95-31.25 μg·mL^-1. In addition to vinegar Bupleuri Radix polysaccharides with molecular weight <3.5 kDa, others significantly promoted the phagocytic activity of macrophages, and the activity of polysaccharides with molecular weights >100 kDa were more significant. All molecular weight segments of vinegar Bupleuri Radix polysaccharides significantly inhibited the release of NO in Raw264.7 inflammatory cells stimulated by LPS. CONCLUSION Molecular weight is an important factor affecting the activity of anti-inflammatory and immunomodulatory.