[Objective] To study the immunoregulatory effect of exopolysaccharide (EPS) from Lactobacillus plantarum JLK0142 on the RAW264.7 macrophages and immunosuppressed murine.[Methods] EPS were isolated and purified from the culture medium of L. plantarum JLK0142. The effects of EPS on proliferation, phagocytosis and nitric oxide (NO) secretion of RAW264.7 macrophages were determined by in vitro tests. Then the spleen index, proliferation of T lymphocyte and levels of IL-2 and TNF-α in serum of immunosuppressed mice induced by cyclophosphamide were determined by in vivo tests.[Results] EPS from L. plantarum JLK0142 could improve the proliferation activity of RAW264.7 macrophages in normal state at concentrations between 50 and 800 μg/mL, and significantly improve the phagocytic capacity of macrophages and the secretion of NO. Compared to control mice, the spleen index and T lymphocyte proliferation activity of the immunosuppressed murine were significantly increased in middle-does and high-dose EPS groups, while the levels of IL-2 and TNF-α in serum were also significantly increased in high-dose EPS group.[Conclusion] The EPS from L. plantarum JLK0142 can effectively improve the immune activity of RAW264.7 macrophages and antagonize cyclophosphamide induced immune suppression in mice.