Abstract: Objective To analyze the relationship between change in plasma D-dimer levels and prognosis of dying patients with malignant tumors. Methods The plasma D-dimer levels of 72 malignant tumor patients were measured within 0-4 weeks and 4-8 weeks before their death. The average period between these two tests was approximately 24 days apart，and the results were statistically analyzed. Results In general, the plasma D-dimer level measured in 0-4 weeks was signifi cantly higher than that in 4-8 weeks(P=0.002), with gastrointestinal malignancies having the most signifi cant difference(P=0.004), followed by lung cancer(P=0.028). However, the difference of the D-dimer levels were similar between men and women and among different age groups (P>0.05). Conclusion The plasma D-dimer levels measured at different times could be used to predict the prognosis of dying patients with malignant tumors.