Abstract: Objective To determine the role of high mobility group chromosomal protein N2 (HMGN2) in the development of periodontitis plaque biofilm. Methods Saliva samples were collected before clinical interventions in patients with periodontitis (25 Mild periodontitis, 25 Moderate periodontitis and 25 Severe periodontitis) and healthy controls ( n=25).Following an estimation of dental plaque index,the level of HMGN2 in saliva was determined by enzyme-linked immunosorbent assay (ELISA).The recombinant human HMGN2 protein was purified and tested, its inhibitive effects on Porphyromonas gingivalis (P.g)growth and formation of P.g bioflim were detected by K-B antibacterial annulus and crystal violet staining, respectively. Results The healthy controls had lower levels of HMGN2 in saliva than those with periodontitis,especially those with severe periodontitis ( P<0.01).The level of HMGN2 was negatively correlated with dental plaque index ( r=-0.363, P<0.05). HMGN2 inhibited the development of main periodontal bacteria biofilm ( P<0.05). Conclusion HMGN2 is involved in the development of periodontitis plaque biofilm and plays an important role in the development of periodontitis.