The invention discloses a power failure time determination method and device based on a power distribution network topological structure. The method comprises the steps of obtaining power failure information of a current line; obtaining zone areas of a first line segment; determining the total power failure times of the zone areas of the first line segment according to the power failure times, which are obtained from the power failure information, of the line where the first line segment is arranged, all the zone areas of the first line segment and the first line segment and a superior line segment of the first line segment; obtaining a second line segment in the current line; determining the total power failure times of the second line segment according to the power failure times, obtained from the power failure information, of the second line segment, a superior line segment of the second line segment and the current line. According to the power failure time determination method and device in the embodiment disclosed by the invention, the power distribution network power failure situation and position can be accurately located by determining the power failure times of the zone areas and the lines.