Background: Vicia amoena Fisch. var. Angusta. Freyn, also known as tuogucao, is a traditional medicinal plant in China. Early researches of V. amoena Fisch. var. Angusta. Freyn were focused on biosystematical studies, and only a few were concerned with chemical constitutes and bioactivities. Objectives: We aimed to isolate chemical constitutes in aerial parts of V. amoena Fisch. var. Angusta. Freyn and study the immunomodulatory activity of these chemical components via immune cells. Materials and Methods: Polysaccharide was obtained via hot water extraction and alcohol precipitation at different concentrations. Individual compounds were obtained after several chromatographic techniques, and the structures of all individual compounds were characterized by physical-chemical process, 1H, 13CNMR, UV techniques and by comparing their NMR data with those discovered in the literature. In vitro immunological activity of tested samples was evaluated using MTT assay, NO assay, scratch assay, phagocytosis assay and proliferation assay of spleen lymphocytes in mice. Results: The four polysaccharide sites including 30%, 50%, 70% and 90% were obtained. Eight pure chemical constitutes were isolated and identified as: isoquercitrin, quercetin, quercitrin, hyperin, chlorogenic acid, kaempferol, kaempferitrin and wogonin. Four polysaccharide sites and individual compounds displayed different levels in improving proliferation and phagocytosis of RAW264.7 macrophages and lymphocytes. Conclusion: Compounds were isolated from the herb that possessed immunomodulatory function, and it is likely that the extract from the herb via the TLR-4-mediated signalling pathway to achieve immunomodulatory effects provided a scientific rationale of the traditional uses of the herb.