Summary Objective: The study aimed to evaluate the risk of death from VTE in severe and critical patients with COVID-19 pneumonia using bilateral lower limb venous ultrasound and D-dimer examination. Methods: In this single-centered, retrospective, observational study, we enrolled 32 adult severe and critical patients with COVID-19 pneumonia who were admitted to the intensive care unit (ICU) of Wuhan Jin Yin-tan hospital (Wuhan, China) between January 1, 2020 and February 20, 2020. All patients underwent bilateral lower extremity venous ultrasound and D-dimer test. The relationship between death of patients and vein thrombosis of bilateral lower extremities, and D-dimer levels was assessed using logistic regression analysis, which was performed including patients’ prognosis as the dependent variable, and sex, age, time to perform bilateral lower extremity venous ultrasound after admission, site of thrombus, mean and standard deviation (SD) of D-dimer levels as independent variables. Results: Among the 32 patients, acute venous thrombosis of both lower extremities occurred in 21 patients, with an incidence of 65.6%. The mortality rate was 52.3% in those patients who developed acute venous thrombosis. Each patient underwent an average of 6 D-dimer tests, 28 (87.5%) had elevated D-dimer levels after each D-dimer test. In the logistic regression analysis, the significant variable was SD for D-dimer levels (P = 0.05), which was included in the final model, the logistic regression equation was as follows: Logit (P) = -29.445+0.367 X6. Conclusion: In order to prevent death from VTE in these patients, bilateral lower extremity venous ultrasound examination should be performed early to identity patients with acute vein thrombosis, and more attention should be paid to the D-dimer level fluctuation during treatment. Keywords: COVID-19; coronavirus; pneumonia; lower extremity venous ultrasound; D-Dimer level; mortality risk; venous thromboembolism; severe/critical conditions