Normal blood flow on Doppler means that there is no pathology in the blood vessels, such as arteriovenous stenosis, malformations, arteriovenous fistulae, or other pathologic factors. Doppler ultrasonography is one of the commonly used clinical examinations to check the speed and direction of blood flow and the distribution of blood flow in the human body, and has a wide range of applications. Doppler ultrasonography is commonly used to examine blood vessels in the heart, cranium, brain, uterus, limbs and other parts of the body to check for hemodynamic changes, which is extremely helpful in clinical diagnosis. It is worth noting that normal blood flow in Doppler examination only means that there is no substantial change in the blood vessels at the examination site, and it does not determine the function of the examination site as a whole, therefore, it is necessary to combine with other examinations to make a comprehensive assessment.