Objective：This study aims to investigate the effect of experimental periodontitis on the expression of reactive oxygen species（ROS） in marrow of mice. Methods：A total of 20 eight-week-old C57BL/6 mice were used in the study，and-experimental periodontitis was induced in mice by thread ligature. After 4 weeks of experiment，the maxilla were undergone micro-CT scanning，HE staining，tartrate-resistant acid phosphatase（TRAP）staining. Flow cytometry was employed to study the expression of ROS in marrow. Results：After four weeks of experimental periodontitis，alveolar bone resorption and TRAP positive osteoclast number were all increased. There were significantly increases of the ROS level in marrow compared with controls. Conclusion：Experimental periodontitis can increase the expression of ROS in mice marrow，which may play regulatory roles in alveolar bone loss.