Objective To explore the value of color Doppler ultrasonography and plasma D-dimer in diagnosis of lower limb deep venous thrombosis (DVT).Methods The clinical data of 70 cases of patients with lower limb DVT diagnosed clinically were retrospectively studied. The lower limb venous of each patient was examined by color Doppler ultrasonography and the plasma level of D-dimer were measured, furthermore the plasma levels of D-dimer in different phase and different type of thrombosis were compared. Results The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of plasma D-dimer and ultrasonography examination in lower limb DVT were 100%, 66.7%, 97.0%, 100%, and 97.1%, and 98.4%, 83.3%, 98.4%, 83.3%, and 97.1%, respectively. The plasma D-dimer in acute phase 〔(6 451±4 012.22) μg/L〕 and subacute phase 〔(2 063±1831.35) μg/L〕 of lower limb venous thrombosis were significantly higher than that in normal control group 〔(310±66.70) μg/L〕, Plt;0.01 and Plt;0.05, which was not different from that in chronic phase 〔(466±350.52) μg/L〕. Meanwhile, the plasma D-dimer in mixed limb venous thrombosis group 〔(4 464±3 753.16) μg/L〕 and central limb venous thrombosis group 〔(2 149±1 911.53) μg/L〕 were significantly higher than that in control group (Plt;0.05 and Plt;0.01), which was not different from that in peripheral limb venous thrombosis group 〔(560±315.62) μg/L〕. Conclusion Color Doppler ultrasonography is an optimal method and the plasma D-dimer is a predictive index in diagnosis of lower limb DVT.