Abstract: Cardiovascular disease is a serious threat to human beings. The inferior vena cava is connected to the right atrium and is the largest vein in human body. Its indicators are particularly important for the auxiliary diagnosis of cardiovascular disease. The inner diameter of the inferior vena is essential for estimating the blood volume and the collapse rate of the inferior vena cava. Therefore, measuring inferior vena cava diameter plays an important role in clinical judgment of various cardiovascular diseases. Based on the characteristics of inferior vena cava vessels in ultrasound images, the inferior vena cava is segmented and tracked to realize the real-time measurement of the inner diameter of the inferior vena cava. In this paper, the OSTU method is firstly adopted to realize threshold segmentation, and then the pre-processed image is obtained by closing operation. The inferior vena cava is segmented based on topological structure analysis. Finally, the position of inferior vena cava is tracked by the optical flow method. The segmentation accuracy of this method reaches 90%～95%, and the difference between the measurement and the gold standard comparison is within 0.25%. This method has significant practical meanings for the prevention and auxiliary diagnosis of cardiovascular diseases such as inferior vena cava sclerosis.