Abstract: OBJECTIVE To explore the change of cellular immunity of diabetic mellitus patients with oral and maxillofacial space infections so as to provide guidance for control of the infections and regulation of body's bad state. METHODS A total of 34 diabetic mellitus patients complicated with oral and maxillofacial space infections who were treated in hospitals from Feb 2013 to Sep 2015 were assigned as the group A, meanwhile, 34 diabetic mellitus patients without oral and maxillofacial space infections were set as the group B, 34 oral and maxillofacial space infections without diabetic mellitus were assigned as the group C, and 34 healthy people who received physical examination were set as the group D.The related serological cellular immunity indicators were compared among the four groups of participants, the test results were compared among the patients in the group A with various degrees of infections and various levels of glycated hemoglobin, and the statistical analysis of data was performed with the use of SPSS 13.0 software. RESULTS The levels of CD₃⁺CD₄⁺, CD₃⁺, CD₄⁺, and CD₄/CD₈ were lower in the group A than in the group B, C, and D, which were lower in the group B and C than in the group D.There was significant difference in the test results among the patients in the group A with various degrees of infections and various levels of glycated hemoglobin (P<0.05). CONCLUSION There is significant change in the cellular immunity of the diabetic mellitus patients with oral and maxillofacial space infections; the degree of infections and level of glycated hemoglobin vary significantly among the diabetic mellitus patients with oral and maxillofacial space infections, to which the great attention should be paid to.