Abstract: OBJECTIVE To explore the effect of Sarcandra glabra injection(SGI) on the expression of costimulatory molecules of U937 cells and its potential mechanism. METHODS The total RNA was extracted when monocytic leukemia U937 cells were treated with different concentration(1.83, 2.75, 3.66, 5.49, 7.32 g·L^-1) of SGI for 48 h. The expressions of costimulatory molecules CD86 and B7-H1 mRNA were detected by RT-PCR. The level of CD86 and NF-κB protein in cytoplasm or intranuclear was measured by Western blotting. RESULTS When treated with SGI for 48 h, the expression of B7-H1 mRNA decreased, the concentration of CD86 protein increased as the concentration of SGI increased, the expression of CD86 mRNA increased when the concentration of SGI were 3.66-7.32 g·L^-1, the concentration of intracytoplasmic NF-κB protein decreased, the intranuclear NF-κB protein increased. CONCLUSION SGI could enhance the expression of CD86 of U937 cells, and reduce the expression of B7-H1. Its mechanisms might be related to the increase of content of intranuclear NF-κB protein.