Objective To study the risk factors of preoperative deep vein thrombosis(DVT)in middle-aged and elderly patients with lower limb fractures,and establish and evaluate the constructed nomogram model.Methods A retrospective analysis was conducted on the clinical data of totally 240 middle-aged and elderly patients with lower limb fractures at Quanzhou First Hospital Affiliated to Fujian Medical University from July 2023 to June 2024.According to whether the patient had DVT before surgery,they were divided into a DVT group of 75 cases and a non DVT group of 165 cases.The differences in clinical data and some labora-tory indicators levels at the time of initial admission,including platelets(PLT),prothrombin time(PT),ac-tive partial thromboplastin time(APTT),fibrinogen(FIB),thrombin time(TT),D-dimer(D-D),total pro-tein(TP),albumin(ALB),triglycerides(TG),cholesterol(CHOL),high-density lipoprotein cholesterol(HDL-C),low density lipoprotein cholesterol(LDL-C)between two groups were compared.Logistic binary regression was used to analyze the risk factors of DVT and a nomogram model was constructed.Receiver oper-ating characteristic(ROC)curve was used to evaluate the diagnostic efficacy of various risk factors and nomo-gram model in screening DVT.Results Compared age and D-D levels of the DVT group were significantly higher(P＜0.001),while the levels of APTT,TP and ALB were significantly lower(P＜0.05),and the pro-portion of DVT combined with internal diseases and the proportion of fractures in the femur were significantly higher(P＜0.001).The above-mentioned differential indicators were all single risk factors for DVT.ROC curve analysis showed that except for comorbidities of internal medicine,all other risk factors could effectively screen for DVT(P＜0.05),the area under the curve(AUC)was 0.573-0.706,and the constructed nomo-gram model could effectively improve AUC to 0.797.Conclusion The nomogram model constructed based on single risk factors for DVT in this study is helpful for clinical assessment of the risk of DVT occurrence in pa-tients at the early stage of admission,intuitively and effectively.