Periodontitis is an infectious, destructive and inflammatory disease of periodontal tissue around teeth. The main clinical manifestations of periodontitis are soft tissue pocket formation, clinical attachment loss and alveolar bone resorption. Visible near-infrared spectroscopy, characterized by noninvasive and rapid detection, has been widely used in medicine. The present study explored the use of visible near-infrared spectroscopy in evaluating the relative contents of oxygenated hemoglobin and deoxyhemoglobin in gingival tissue of severe periodontitis. The gingival tissue spectra (400～1 700 nm) were obtained and processed from 20 sites of 5 healthy subjects and 20 sites of 5 patients with severe periodontitis. Spectra were collected at the gingival margin, 4 and 7 mm below the gingival margin. Our research found that oxygenated hemoglobin and deoxyhemoglobin showed obvious spectral absorption characteristics at 544 and 576 nm respectively. The relative absorption depths of oxygenated hemoglobin and deoxyhemoglobin were calculated from the continuum removal based on the original spectral data. The results showed that the relative contents of oxygenated hemoglobin and deoxyhemoglobin in the periodontal pocket of severe periodontitis were significantly higher than those in the healthy group (p<0.05). At the same time, there was no significant difference in the contents of oxygenated hemoglobin and deoxyhemoglobin at different depths in the deep periodontal pocket of severe periodontitis. The results reflected the hemodynamic differences between severe periodontitis and healthy gingival tissue, and provided a scientific basis for applying visible near-infrared spectroscopy in noninvasive detection and auxiliary diagnosis of periodontitis.