Abstract: Patients undergoing cardiac surgery generally have a high risk of hypotension-related complications, which was attributed to the patients’ serious condition and the technical difficulty of the surgery. Previous studies have confirmed that postoperative hypotension affects the prognosis. Therefore, early diagnosis of postoperative hypotension is of great significance to improve the clinical symptoms and prognosis of patients. Ultrasonography can dynamically evaluate the anatomical structure and physiological function of the cardiovascular system and can detect the hemodynamic status contemporaneously. In addition, ultrasonography has the advantages of implementation at most conditions and can even be performed at the bedside. In its clinical application, a series of new consensuses and new technologies have been developed to improve the diagnosis of postoperative hypotension, which can help cardiologists to evaluate the causes and severity of postoperative hypotension in multiple dimensions. This article described the incidence of postoperative hypotension and the diagnostic and predictive efficacy of ultrasound for postoperative hypotension, in order to provide a theoretical basis for surgical treatment and postoperative management of cardiovascular diseases.