Abstract: Objective: By comparing the image quality of the inferior vena cava (IVC) direct CT venography (CTV) using multi-detector computed tomography (MSCT), under different contrast medium injection rate conditions, to obtain optimal contrast medium injection rate, Methods: Using 64-detector row scanner (Sensation 64; Siemens), 30 patients who were suspected of inferior vena cava diseases underwent IVC direct CTV examination. Randomly divided into 5 groups, at the same conditions of contrast medium concentration (1: 6), liquid volume (unilateral liquid volume 200 mL), delay scan time (30 s) and without ligation of superficial veins of lower limbs, the contrast medium injection rate of each group was 2.5, 3.0, 3.5, 4.0, 4.5 mL/s respectively, then compare the image quality of each group. Result: All patients successfully completed the examination, the image quality of contrast medium injection rate 3.5~4.0 mL/s group is better than others, satisfied with clinical diagnostic purpose. Conclusion: IVC direct CTV using MDCT is feasible, at the same conditions of contrast medium concentration (1: 4), liquid volume (unilateral liquid volume 200 mL), and delay scan time (30 s) and without ligation of superficial veins of lower limbs, the optimal contrast medium injection rate is 3.5~4.0 mL/s.