The invention discloses a method for determining the reliability of a power communication system. The method comprises the following steps of: (1) establishing a network model of the power communication system required to be detected, and acquiring an undirected connected graph; (2) calculating the node reliability corresponding to each node according to the node level and the attribute data of communication equipment; (3) calculating the link reliability corresponding to each optical cable according to the attribute data of optical cables; (4) calculating the link integrated reliability of each series system according to the node reliability and the link reliability; (5) solving the betweenness of each link, and calculating the clustering reliability of each node according to the link integrated reliability and the link betweenness; and (6) calculating the clustering reliability mean of the power communication system according to the clustering reliability of each node, and determining the reliability of the power communication system according to the clustering reliability mean. By adopting the method for determining the reliability of the power communication system, the determining result is high in accuracy, and the actual reliability of the power communication system required to be determined is objectively reflected.