Objective To explore the influence of different preservation methods, preservation time and hemolysis in the detection of myeloperoxidase (MPO). Methods Blood samples were collected from the 30 patients. Everyone collected three blood samples, which were anticoagulated by heparin sodium. The first tube separated the plasma in 30 minutes, and then plasma MPO were assayed and considered as base line value. The remaining two samples were divided into two groups, one group was stored at the room temperature (22°C) for 4 hours, and the other was stored at refrigerator (2-8°C) for 4 hours. The MPO were detected. The first tube plasma of 15 patients were screened and respectively preserved in 2-8°C and -20°C, according to which, the samples were divided into two groups. The MPO was assayed at 1, 3, and 5 days. Results The MPO levels in samples stored at the room temperature and refrigerator at 4 hours was increase but without significant statistical differences in two groups (P>0.05). The MPO levels in samples stored at 2-8°C and -20°C was decreased as the storage time prolong (P<0.01). The degrees of hemolysis had a substantial impact on analysis of MPO. Conclusion The blood samples should be used for MPO detection immediately after sampling. The hemolysis has a substantial impact on analysis of MPO.