Natural polysaccharides and their modified derivatives are crucial supplements to the prevention of inflammation. This study aimed to evaluate the effect of sulfated modification on the anti-inflammatory and anti-oxidative activities of Cyclocarya paliurus polysaccharides (CP). A sulfated CP, S-CP 1–4 was obtained using chlorosulfonic acid-pyridine method. The chemical components and FT-IR spectrum confirmed that sulfated group was synthesized to the polysaccharide chains successfully. S-CP 1–4 was found to inhibit nitric oxide production, phagocytic activity and the release of interleukin (IL)-6 and IL-1β in lipopolysaccharide-treated macrophage cells, RAW 264.7. S-CP 1–4 significantly decreased the secretion of IL-6 and TNF-α and the thymus and spleen indexes, and increased the production of IL-10 in lipopolysaccharide-treated mice. S-CP 1–4 could better protect the liver by inhibiting the activities of alanine aminotransferase and aspartate aminotransferase, and malondialdehyde level while increasing the superoxide dismutase activity and total anti-oxidative capacity. These results suggested that S-CP 1–4 may be an effective anti-inflammatory agent, and sulfated modification may be a reliable method for the development of food supplements.