Objective To detect the biochemical reactions and analyze the carbohydrate metabolism of Porphyromonas gingivalis (P.gingivalis) clinical isolates, with type strains as controls. Methods API 20A and ATB Rapid ID 32A biochemical reaction testing systems were used to determine the biochemical metabolic properties of P.gingivalis clinical isolates (SJD2, SJD4, SJD5, SJD11 and SJD12), with type strains (W83 and ATCC 33277) as controls. Results All tested P.gingivalis strains possessed enzymatic activity of β-galactosidase and β-N-Acetyl-glucosaminidase. These strains had capacities to hydrolyse several amino acid residues and free amino acids such as tryptophan and arginine. In addition, there existed heterogeneity in the biochemical reactions among P.gingivalis strains. Furthermore, different bacterial identification results were found between API 20A biochemical reaction testing system and ATB Rapid ID 32A biochemical reaction testing system. Conclusion P.gingivalis may utilize peptides and amino acids as main carbon or nitrogen resources, with the ability of metabolizing carbohydrate. There are differences in biochemical properties among different strains. ATB Rapid ID 32A test system may be more suitable for identification of gram-negative subgingival anaerobes.