(20S*,24R*)-epoxy-9,19-cyclolanstane-3β,12β,16β,25-pentaol-3-O-β-D-xylopyranoside (BC1) is a kind of natural bioactive substance extracted from Beesia calthaefolia (Maxim.)Ulbr. This study was designed to evaluate the effects of BC1 on the proliferation of lymphocytes, phagocytosis of peritoneal macrophage, and cytokine secretion, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and the foot pad thickness index, which is beneficial for understanding the mechanism of BC1 on immunoregulation and anti-inflammation and also will benefit our further research. The proliferation of splenic lymphocyte induced by mitogen (concanavalin A or lipopolysaccharide (LPS)) was detected using the cell counting kit assay. The neutral red phagocytic test of macrophages was determined by colorimetric method. The gene and protein expressions of TNF-α and IL-1β were measured by real time RT-PCR and ELISA in serum, spleen, and lymphocytes, respectively. In vitro, our present study has shown that BC1 (31.25-250 μg/ml) could inhibit the proliferation of splenic lymphocyte and phagocytosis of macrophages, and inhibit the increased production of TNF-α and IL-1β in protein and gene levels. In mice, LPS could increase the gene and protein expressions of TNF-α and IL-1β, respectively, but BC1 (12.5-50 μg/kg) could recover the increased gene and protein expressions of TNF-α and IL-1β induced by LPS in the spleen and serum of mice. Treatment of arthritic rats with BC1 (1.5 mg/kg body weight) resulted in a significant reduction in foot pad thickness index and serum TNF-α level comparable to the indomethacin-treated arthritic rats, proving its anti-inflammatory effect. Thus, the function of immunoregulation of BC1 may be accomplished through modulating the gene and protein expressions of TNF-α and IL-1β.