Terahertz (THz)-wave has brought huge application prospect to the study of basic disciplines, medical imaging and nondestructive testing, for its unique features in spectrum and transmission performance, and it has significant scientific strategic importance. The development process of THz-wave parametric oscillator (TPO) is mainly summarized from several aspects: nonlinear crystals used in THz generation, resonator structures including external cavity, intra-cavity and pump-enhanced cavity, THz wave output coupling schemes, surface-emitted structure, pump light parameters and injection seeding. With the development of new materials and new structures, TPO will play an important role in more fields.