Developments of contrast agent and imaging technique have made it possible for using contrast-enhanced ultrasound (CEUS) to assess perfusion. As an irradiative, real time and repeatable technique, ultrasound is revealing its advantages in this field compared with nuclear medicine, CT and MRI. This paper introduces the mechanism and methods of the CEUS in the perfusion ultrasound. The advancement in the study of the time-intensity curve (TIC) in systemic organs is also reviewed in this paper.