As the resources of transmission corridors become increasingly scarce，UHV hybrid multi-terminal DC transmission systems are expected to become the mainstream trend in the development of DC transmission systems. Reliability assessment of them has become a very important part of power system planning，design and operation. First，the reliability evaluation model of the UHV hybrid multi-terminal DC transmission system is established，and then the reliability evaluation algorithm based on the characteristic parameter matrix is proposed to realize the reliability evaluation of UHV hybrid multi-terminal DC transmission system. Finally，based on relevant calculation examples，the proposed method and conventional method are used to evaluate and analyze the reliability respectively. According to the comparison of the reliability evaluation calculation results，the efficiency and accuracy of the proposed method are verified. For complex UHV hybrid multi-terminal DC transmission，the system has good applicable value.