Hybrid HVDC is a new topology which contains line commutated converter (LCC) and the voltage source converter (VSC). This paper discusses the technical characteristics of flexible HVDC, multi-terminal high-voltage DC (MTDC), and Hybrid HVDC. And it offers an application method of the multi-terminal Hybrid HVDC transmission System, which has large capacity, complicated operation mode and high reliability. Control and protection technology, which is the core of MTDC, is the base of the normal and stable operation of MTDC system. MTDC's control and protection strategy is closely related to the type of inverter, connection mode, transmission distance, system size and operation requirements. In this paper, the three-terminal hybrid DC transmission is taken as an example, the control and protection technology of UHVDC transmission system is described. Besides, it describes the suitable situations, technical characteristics and the related implementation methods of the Hybrid HVDC.