This study was aimed to investigate the value of neutrophilic CD64 index (nCD64 index) as a diagnostic marker of bacterial infection in hematologic diseases. Experimental data of 232 patients with hematologic diseases were analyzed retrospectively. The nCD64 index was detected by flow cytometry and was compared with the levels of erythrocyte sedimentation rate (ESR), C reaction protein (CRP) and fibrinogen respectively. The results showed that the nCD64 index in clinical infection group were significantly higher than that in non-infection group and autoimmune disease group (P < 0.0001 respectively). The nCD64 index in blood culture positive group was also significantly higher than that in blood culture-negative group (P < 0.01). The result of ROC curve analysis showed that the optimal critical values of nCD64 index, ESR, CRP and Fib were 4.96, 21.5 mm/h, 8.56 mg/dl and 4.42 mg/dl, respectively. The sensitivity and specificity of nCD64 index were 0.928 and 0.933, while the sensitivities of ESR, CRP and Fib were 0.725, 0.754 and 0.594, and the specificities of CRP, ESR and Fib were 0.625,0.837 and 0.77, respectively. It is concluded that nCD64 index is possessed of much higher in sensitivity and specificity, compared with ESR, CRP and Fib in diagnosis of bacterial infection of hematologic diseases. nCD64 index can be used as an effective diagnostic marker for bacterial infection of hematologic diseases.