Three undescribed isosteroidal alkaloids (1-3), along with two known ones (4, 5) were isolated from the bulbs of Fritillaria ussuriensis Maxim, their structures were established by comprehensive analyses of the 1D, 2D-NMR and HR-ESI-MS data. Meanwhile, LPS-activated RAW 264.7 macrophages were used to determine the potential antiinflammatory activity of all the alkaloids in vitro. Among them, compounds 1 and 4 showed significant inhibitory effects against LPS-induced NO production with IC50 values of 7.79 mu M and 11.22 mu M, respectively. Compounds 1 and 4 were performed between molecular docking with TLR4/MD2. Based on the results of cell experiments and binding affinities, compound 1 (UG) was chosen for molecular dynamic analysis together with the TLR4/MD2 protein.