Abstract: OBJECTIVE To investigate the diagnostic value of neutrophil CD4 (nCD4) in peripheral blood on leukemia patients with bacterial infection,so as to provide the assistance for clinical treatment. METHODS A total of 100 leukemia cases and 100 healthy subjects were selected for the study, and were divided into leukemia group and control group. Leukemia patients were divided into leukemia infection group and leukemia uninfected group according to whether had clinical infection, and bacterial infection patients were divided into blood culture positive group and blood culture negative group according to blood culture results. The average fluorescence intensity of nCD4 in peripheral blood was determined by flow cytometry, the level of procalcitonin (PCT) was measured by electrochemiluminescence method, and C-reactive protein(CRP) level was measured by immunoturbidimetry. RESULTS The nCD4 fluorescence intensity (183.24±67.35,44.25±25.46), PCT level (10.43±1.21 ng/ml, 3.25 ± 0.42 ng/ml), and CRP level (72.35±15.34 mg/l, 14.32±3.24) in leukemia infection group and leukemia uninfected group were significantly higher than those in control group (26.87±12.43, 0.42±0.13 ng/ml, and 2.12 ± 0.09 mg /l), and the differences were statistically significant (P<0.05). The fluorescence intensity of nCD4 in blood culture positive group was (247.76±76.23), which was higher than (154.24±54.45) in blood culture negative group, and the difference was statistically significant (P<0.05). The sensitivity of nCD4, PCT and CRP in the diagnosis of leukemia bacterial infection were 91.8%, 79.8%, and 82.4%,and the specificity were 79.7%, 75.8%, and 77.1%, respectively. The sensitivity and specificity of nCD4 in the diagnosis of leukemia bacterial infection were higher than those of PCT and CRP. CONCLUSION nCD4 can predict leukemia bacterial infection in a certain extent, and can be used as a diagnostic indicator for leukemia patients with bacterial infection.