Abstract: Objective: To explore the significance of the changes of blood coagulation index in patients with malignant blood system diseases.Methods: The difference of the blood coagulation index in 135 patients with malignant neoplastic hematologic disorder was analyzed retrospectively,and the changes of the blood coagulation index in patients with acute leukemia (AL),chronic leukemia (CL),lymphoma and multiple myelomaly were summarized.Results: The prothrombin time (PT),activated partial thromboplastin time (APTT),D-dimer (D-D) and fibrin degradation product (FDP) in patients with AL,lymphoma and multiple myelomaly were significantly different from those of the normal control (P<0.05-P<0.01);the PT,APTT,D-D and FDP between M3 sabutype AL and non-M3 abutype AL in patients with acute lymphoblastic leukemia differed significantly (P<0.05) compared with those in other groups;the fibrinogen (FIB) presented no significant difference among the groups (P>0.05).The blood coagulation index in patients with lymphoma was not statistically different (P>0.05).Conclusions: The coagulation and fibrinolysis are abnormal in patients with hematological malignancy.Detection of FIB,D-D and FDP may help to judge whether the patients are in a state of hypercoagulability,which will provide basis for early intervention;detection of PT and APTT may provide evidence for the occurrence of disseminated intravascular coagulation and the application of clinical medication.