Abstract: Objective: To investigate the effect of carotid artery bifurcation anatomy and hemodynamics on wall shear stress by using ultrasound vector flow imaging (V Flow) technique. Methods: A total of 70 normal patients after carotid artery ultrasound examination were selected as the study subjects. By placing the V Flow region of interest at the bifurcation of the carotid artery, the ratio (D_CB/D_CCA) of the inner diameter of carotid bulb (D_CB) where the area is the most obvious expansion at the end-systolic to the inner diameter of terminal segment of common carotid artery (D_CCA), the angle (θ) between the carotid bulb and the common carotid artery, and the ratio (Q_CB/Q_CCA) of the blood flow of the carotid bulb (Q_CB) to the terminal segment of common carotid artery (Q_CCA) were measured. And the visualized area of blood flow disorder in the carotid bulb (ACB) was recorded and the average shear stress of the inner wall ＆ outer wall of the carotid bulb was measured. All the above parameters were analyzed by statistical method. Results: (1) The WSSI-CB value of the inner wall of the carotid bulb was (0.88±0.30) Pa, and the WSS_E-CB value of the outer wall was (0.32±0.15) Pa, the WSSE-CB value of the outer wall was significantly smaller than the WSSI-CB of the inner wall, and the difference was statistically significant (P<0.01). (2) The angle between the carotid bulb and the common carotid artery was (24.5±12.1)°, and its correlation coefficient with WSS_E-CB was r =-0.171, i.e. there was no correlation between them, their difference was not statistically significant (P>0.05). The ratio of the most obvious enlargement of carotid bulb to the inner diameter of common carotid artery (D_CB/D_CCA) was (0.66±0.09), which was negatively correlated with WSS_E-CB value, the correlation coefficient r =- 0.312, and their difference was statistically significant (P<0.05). (3) The ratio of the volume of carotid bulb to the volume of terminal carotid artery (Q_CB/Q_CCA) was (0.69±0.15), which was positively correlated with WSS_E-CB value, the correlation coefficient was r =0.428, and their difference was statistically significant (P<0.01). The area of blood flow disorder in the carotid bulb (A_CB) was (0.27±0.17) cm², which was negatively correlated with WSS_E-CB value, the correlation coefficient was r= - 0.545, and their difference was statistically significant (P<0.01).Conclusions: The blood flow of internal carotid artery, the area of the bifurcation where the blood flow is diffuse and amorphous, and the degree of bulbar enlargement are the main factors affecting the lateral wall WSS, but it is not closely related to the angle of the internal carotid artery.