Pulse wave velocity in an artery is a very important indicator of the stiffness and disease of the artery. Pulse wave velocity in an artery is measured with the standard pulse delay technique. However, the precise timing of the pressure wave is difficult due to the presence of reflected waves. In this paper we propose to generate a wave of a few hundred Hz in an artery by localized radiation force of ultrasound. This wave attenuates very quickly, in a few centimeters, due to the viscoelasticity of the artery and surrounding tissues. Therefore, no reflected wave exists. The wave velocity can be measured accurately by the phase change versus distance. The frequency dispersion of wave velocity is also described because the pulse wave velocity method does not consider dispersion. A new theoretic model is proposed to investigate the wave propagation in arteries. The model is substantiated by in vitro experiments.