This study was purposed to investigate the immune state of the patients suffered from pulmonary infection within 6 months after haploidentical hematopoietic stem cell transplantation (hi-HSCT). Adenosine triphosphate (ATP) value in CD4(+) T cells was measured by ImmuKnow method to assess the function of the lymphocytes in peripheral blood of 25 patients at 6 months after hi-HSCT. The results showed that the ATP level in CD4(+) T cells of the patients suffered from pulmonary infection was (179.88 ± 65.41) ng/ml before transplantation, (172.69 ± 118.81) ng/ml at 1 month, (218.15 ± 124.26) ng/ml at 3 months, (313.42 ± 116.29) ng/ml at 6 months after transplantation. The ATP level in CD4(+) T cells of the patients without pulmonary infection was (210.44 ± 94.71) ng/ml before transplantation, and decreased to (193.66 ± 133.69) ng/ml at 1 month and increased gradually to (355.02 ± 43.38) ng/ml at 3 months, (355.73 ± 93.85) ng/ml at 6 months after transplantation. It is concluded that the low ATP value in CD4(+) T cells in patients prior and post hi-HSCT may suggest probability of occurrence for infections, ATP value in CD4(+) T cells may be used as a reference indicator for clinical empirical use of antibiotics.