Objective To investigate the effects of lipopolysaccharide (LPS) on the expression of matrix metalloproteinases-13 (MMP-13) in mouse osteoblast MC3T3-E1 and their molecular mechanism. Methods The osteoblast MC3T3-E1 of subculture mouse was treated by LPS. Expressions of MMP-13 and transcription factor C/EBPβ, nuclear factor-κB (NF-κB) and its inhibitory protein IκB, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in MC3T3-E1 cells were detected by the Western blotting. The effects of specific inhibitor Bay11-7082 of NF-κB and expressions of specific siRNA silencing C/EBPβ, TNF-α, and IL-6 on the expression of MMP-13 in MC3T3-E1 cells were observed. Results The results of Western blotting showed that LPS induced high level expression of MMP-13 in MC3T3-E1 cells, promoted the expression and activation of NF-κB, C/EBPβ, and IL-6, and inhibited the expression of IκB. Expressions of TNF-α and MMP-13 in MC3T3-E1 cells could be effectively inhibited by Bay11-7082 and siRNA silencing TNF-α. While the siRNA silencing C/EBPβ and the expression of IL-6 did not significantly influence the expression of MMP-13 in MC3T3-E1 cells. Conclusion LPS can induce high level expression of MMP-13 in osteoblast MC3T3-E1 by NF-κB/TNF-α, which helps clarifying the pathogenesis of periodontitis.