The invention provides a power distribution network line fault risk day prediction method and system. The method comprises steps that the external environment information of the location area of a tested line on the prediction date, load prediction data of the tested line on the prediction date, an operation plan of the tested line on the prediction date and the self status information of the tested line on the prediction date are acquired; the acquired external environment information of the tested line on the prediction date, the acquired load prediction data of the tested line on the prediction date, the acquired operation plan of the tested line on the prediction date and the acquired self status information of the tested line on the prediction date are inputted to a pre-constructed line fault risk day prediction model, and a fault generation probability prediction value of the tested line on the prediction date is generated. The method is advantaged in that based on line load prediction, weather prediction, the operation plan, the line operation environment and other situations, line fault risk day prediction is carried out, so relevant fault avoidance measures are adopted, fault generation is avoided, and power supply reliability is guaranteed.