The invention discloses a power supply reliability evaluation method and system. The influences of a power distribution network grid structure on reliability indexes are classified into three categories, namely, links, connections, and mutual influences. Existing reliability evaluation algorithms cannot perform quantitative analysis on the influences on the reliability indexes from the three aspects. The evaluation method of the present invention includes steps of matrix construction, model establishment and index calculation. The matrix construction aims to generate a topology matrix of a power distribution network grid structure; according to the model establishment, a calculation model of the reliability indexes is built through using the topology matrix; and according to an index calculation unit, the calculation model of the reliability indexes is adopted to calculate the reliability indexes, and the influences of the links, connections, and mutual influences on the reliability indexes are expressed in a quantified manner. With the method and system of the invention adopted, the quantitative indexes of power distribution network user reliability analysis and system reliabilityanalysis are realized, and the influences of the links, connections, and mutual influences on the reliability indexes are reflected.