The invention relates to a method for estimating the operation risks of a unit-system power distribution network, and belongs to the technical field of power system intelligent analysis and control. The method comprises the steps: dividing a power distribution network structure into a plurality of units according to the unit-system power distribution network planning and reconstruction which is strongly promoted currently, taking a power supply unit as the minimum logic analysis unit for the analysis of the operation risks of the unit-system power distribution network, and obtaining a model and an operation mode for a power distribution network in a power supply logic unit; quantitatively estimating the occurrence probability and severity of each risk factor based on a risk matrix, and constructing an operation risk estimation index system of the unit-system power distribution network; and finally carrying out the risk rating of the calculated grid risk estimation indexes after the analysis of the power distribution network risks of each logic unit. According to the invention, the method facilitates the automatic recognition of weak links of a power distribution network in a unit grid, can achieve the advanced prevention of the bigger risk items, reduces the damages to the unit-system power distribution network, and improves the power supply reliability for a user.