Abstract: Lead perovskite relaxor piezoelectric single crystals (SCs) are ABO₃ type piezoelectric materials that have lead (Pb) at the A site and complex oxides such as niobium (Nb), magnesium (Mg), zinc (Zn), indium (In), and titanium (Ti) at the B site and their material development and application began in early 1980s. These kind of relaxor SCs in the rhombohedral (R) phase with the PT composition close to the morphotropic phase boundary (MPB) have been studied systematically, since they have ultrahigh piezoelectric coefficients d₃₃ and electromechanical coupling coefficients k₃₃ compared with the traditional Pb(Zr,Ti)O₃ (PZT) ceramics. At present, seven companies are mass-producing and selling these SC materials in the world for piezoelectric probes of medical ultrasonic diagnostic apparatuses. In this article, we will introduce the history and current situation of the lead perovskite piezoelectric SCs, and the alternating current poling (ACP) method, which has been a big topic in recent years in detail.