Abstract: Objective To analyze the risk factors for lower extremity deep venous thrombosis (LDVT) and establish its clinical scoring system. Methods Clinical data about 677 patients with suspected LDVT in lower extremity admitted to our hospital from October 2010 to November 2010 were retrospectively analyzed. Eleven risk factors were assessed according to their grading. OR value of each factor was calculated. A quantitative grading system was established according to the comprehensive score of each patient. Results The incidence of LDVT in lower extremity was 11.34%, 12.63%, 18.18%, 26.23%, 30.65%, 36.84%, 40.31%, 52.08%, 57.78%, 64.44%, and 81.58% respectively in the patients with a risk factor score of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. A score of 7 as shown on ROC curve could show the best point in lower extremity with or without LDVT. A grading system with a score ≤3, 4-6 and ≥7 was established for mild, moderate and severe LDVT, respectively. Conclusion The LDVT risk scoring system we established in this study can provide preliminary and reliable evidence for the clinical assessment of risk factors for LDVT in lower extremity.