The invention relates to a method for reliability evaluation of full voltage classes. The method for reliability evaluation of full voltage classes comprises the steps that a power grid topology is analyzed, a power grid is divided into a power generation system, a power transmission system, a transformer substation main connecting wire and a power distribution system, reliability evaluation is conducted on the power generation system and the power transmission system when the power generation system and the power transmission system are in full load condition, the node reliability indexes of the power generation system and the power transmission system are taken as equivalent source parameters of the power distribution system, a transformer substation main connecting wire equivalent model is established and added to the power distribution system, the reliability index of the power distribution system is determined according to the minimum cutest method, and the reliability index of the full voltage classes is determined finally. By the adoption of the method for reliability evaluation of full voltage classes, reliability evaluation of the full voltage classes can be achieved, and the level of reliability evaluation of a power system is increased.