Abstract: Objective To analyze the common outer membrane proteins (OMP)from Porphyromonas gingivalis (Pg)by surface enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) and to provide antigens for the subsequent experiments in screening vaccine for periodontitis therapy. Methods Four strains of Pg were cultured under anaerobic conditions. The common OMP was extracted through ultracentrifugation and SELDI-TOF-MS was employed to detect the expressions of proteomes by chip H50. The data was analyzed by Biomarker Wizard. ResultsFour kinds of strains of OMP fingerprint spectrum were obtained. Seventy-one proteins of PgATCC33277, 74 proteins of PgW83, 76 proteins of PgW301 and 72 proteins of Pg381 were captured by chip H50. Thirteen common proteins were identified according to fingerprint spectrum. There was only 1 of the 13 common proteins identified in NCBI protein bank. ConclusionsSELDI-TOF-MS has good reproducibility and high sensibility and can be used to identify the common OMP of Pg. The 13 proteins have a potential value in the screening vaccine candidate antigen sites for periodontitis.