Objective To analyze the characteristics of plasma D-dimer, fibrin degradation products (FDPs) and other coagulation indices in patients with coronavirus disease 2019 (COVID-19) pneumonia and explore their predictive value for patient′s condition. Methods A total of 100 patients with COVID-19 pneumonia admitted to our hospital from December 7,2022 to January 28,2023 were enrolled and then divided into mild (n=29), moderate (n=40), and severe/critical infection (n=31) groups. Their plasma D-dimer, FDPs and other coagulation indices were recorded, and the characteristics of coagulation indices were analyzed in the three groups. SPSS statistics 27.0 was used for statistical analysis. LSD-t test, Fisher exact test, Kruskal-Wallis test, χ²test or Bonferroni calibration test were employed for intergroup comparison depending on data type. Receiver operating characteristic (ROC) curve was plotted to evaluate the diagnostic value of FDPs, D-dimer, age, and their combination in predicting mortality in the COVID-19 infected patients. Results Larger proportions of older age and comorbidities and higher mortality were observed in the severe/critical groups than the mild and moderate groups (P<0.05). Plasma FDPs level in the moderate group and plasma FDPs and D-dimer levels in the severe/critical group were significantly higher than those in the mild group (P<0.05). The area under the curve (AUC) of FDPs, D-dimer, age, combined FDPs and D-dimer, and combination of FDPs, D-dimer and age in predicting mortality in the COVID-19 infected patients was 0.785 (95%CI 0.645-0.926; P<0.01), 0.811 (95%CI 0.691-0.03; P<0.01), 0.725 (95%CI 0.558-0.891; P<0.05), 0.766 (95%CI 0.581-0.951; P<0.05) and 0.875 (95%CI 0.789-0.962; P<0.01), respectively, and the sensitivity was 90.9%, 100.0%, 72.7%, 81.8% and 100.0%, and the specificity was 61.8%, 50.6%, 78.7%, 71.9% and 62.9%, respectively. Conclusion Plasma D-dimer and FDPs levels are significantly increased in COVID-19 patients. The two indicators combined with advanced age have an important predictive value for the severity and poor prognosis of COVID-19.