For the miniaturization of microelectronics, carbon nanotubes (CNTs) are regarded as ideal candidates for the next generation of nanoelectronics because of their excellent properties. To realize CNT-based electronics, intramolecular junctions are required components, which can not only connect different CNTs for integration, but can also act as functional building blocks in the circuit, such as rectifiers, field-effect transistors, switches, amplifiers, photoelectrical devices, etc. Therefore, intense attention has been focused on this topic and many advances have been achieved, especially in recent years. On the other hand, some challenges also exist. To provide researchers with a comprehensive overview of this field, this review discusses the synthesis, properties, and applications of intramolecular junctions of CNTs in detail. Among them, the applications of CNT integration are discussed specially. Furthermore, a brief summary and an outlook of future work are provided.