Abstract: OBJECTIVE To investigate the infection source, complication and risk factors of oral and maxillofacial space infection (MSI) , so as to provide the basis for clinical diagnosis and treatment of MSI infection. METHODS A total of 120 patients with MSI from Jan. 2014 to Dec. 2015 in the First People's Hospital of Yongkang were selected as the subjects, and the clinical data of the patients were collected. RESULTS The infections of MSI included 67 cases of odontogenic infection (55.8%) and 53 cases of non-odontogenic infection (44.2%). Odontogenic infection included 27 cases of periapical periodontitis (22.5%), 23 cases of wisdom tooth crown perianitis (19.2%), 16 cases of periodontal disease (13.3%), and 1 case of other disease(0.8%). Non-odontogenic infection included 16 cases of glandular infection (13.3%), 14 cases of non-specific lymphadenitis (11.7%), 13 cases of skin infections (10.8%), 6 cases of osteomyelitis (5.0%), and 4 cases of other diseases (3.3%). The results showed that 65 cases were infected with pathogenic bacteria, 45 cases of which were single infection, 20 of which were mixed infection, and 85 strains were co-cultured. The main pathogens were 24 strains of Klebsiella pneumoniae (28.2%), 19 cases of Streptococcus viridans (22.4%),19 cases of Staphylococcus aureus (22.4%), and 18 cases of anaerobes (21.2%).In the 120 cases of patients, 18 patients had complications, among which, 12 patients had upper respiratory dyspnea, 3 patients had pneumonia, 2 patients had pleural effusion, and 1 patient had respiratory failure. Univariate analysis showed that the incidence of complications in patients with diabetes, white blood cell count ≥15×10⁹/L, multi-gap infection (24.4%, 26.3%, 39.1%) were higher than those without diabetes, white blood cell count <15×10⁹/L, single-gap infection (10.1%, 9.8%, 9.3%) (P<0.05). Multivariate analysis showed that white blood cell count ≥15× 10⁹/L and multi-gap infection were independent risk factors for complications (P<0.05). CONCLUSION MSI infection is mainly caused by odontogenic infection, the main pathogens are Streptococcus viridans and Klebsiella pneumoniae, and the white blood cell count ≥ 15 × 10⁹/L and multi-gap infection are independent risk factors for MSI complications.