The invention relates to the technical field related to direct-current power transmission systems, in particular to a direct-current power transmission system reliability evaluation method. The method includes: obtaining channel equivalent outage hour of a direct-current power transmission system within a preset counting period; calculating the percentage of the channel equivalent outage hour accounting for the counting period as the channel operating unavailability; calculating the channel operating availability according to a formula that the channel operating availability equals to one plus the channel operating unavailability; and adopting the channel operating availability to evaluate reliability of the direct-current power transmission system. The direct-current power transmission system reliability evaluation method is more scientific, and when an available time proportion of the direct-current power transmission system within the counting period is calculated by adopting the channel operating availability, level of influences on the whole power grid caused by the unavailable operating state of the direct-current power transmission system at each time is additionally taken into consideration by means of weighting, so that defects of original energy availability indexes are overcome to a great extent.