With the gradual integration of large-scale new energy, hybrid multiple sending terminals HVDC (H-MSTDC) system gradually develops from single terminal structure to multiple sending and receiving terminals. The operation mode of multiple converter stations and capacity allocation among converter stations increase the complexity of reliability evaluation. The typical connection structure and operation mode of H-MSTDC system are analyzed by considering the capacity distribution coefficient among converter stations in multiple sending terminals and receiving terminals, and the comprehensive reliability index of each receiver and system of H-MSTDC system is constructed. The reliability evaluation model is proposed based on subsystem division and uniform design method. Finally, based on the alternative connection structure of a two-sending and two-receiving project in southeast Tibet and considering the capacity allocation coefficient, the reliability evaluation of H-MSTDC system is carried out, and the variation trend of system reliability under the influence of extreme geographical environment is analyzed, which can provide reference for practical projects.