Aim To probe a simple, convenient, non-invasive and credible method to measure people's carotid artery, and to provide an early way to prevent and cure stroke. Methods High differentiate ultrasonic system was used in our research to measure 53 cases with high risk of stroke and 53 healthy cases. The changes of inner-diameter of carotid artery were measured at relaxation, reactive congest and after taking glonoine. Results The ultrasonic audio image showed that inner membrane incrassated and lumen diminished in high risk of stroke group, in reactive congest test and after taking glonoine, carotid artery dilated notably in healthy group. Conclusion Endothelia dependent diastolic function of carotid artery were adjustive remarkably in healthy people. With the flow of blood stream raised, the endothelia dependent dilatation increased in healthy group; the power of regulating of carotid artery dropped observably in high risk of stroke group. The research also indicated that this measure is simple, convenient and credible.