Objective:To investigate the immunomodulatory effect of Astragalus Saponin on macrophages and explore the mechanisms of its immunomodulation.Methods:By adding different concentrations of AS into cultured mice peritoneal macrophages,the influence of AS on synthesis of nitro oxide(NO)was observed by NO Kit(enzymic method).MTT assay was used to determine the cytotoxicity of macrophages induced by AS.The morphological changes of the macrophages were identified by Transmission Electron Microscope.LSCM and specificity fluorescent probe Fluo-3/AM were applied to observe the change of Ca2+ in the macrophages induced by AS.Results:AS could significantly increase NO synthesis,enhance the capacity of mice peritoneal macrophages for cytotoxicity to carcinoma cells.The surface projections of the macrophages were exhibited multiplicating,thickening and extenting via Transmission Electron Microscope.Augmented intracellular Ca2+ in the macrophage was observed by LSCM.Conclusion:AS can enhance the immune functions of macrophages,the increase of intracellular Ca2+ be one of the mechanisms of its immunomodulatory effects.