The invention provides a power distribution protection method and device of a power grid, and relates to the technical field of a power system. The method comprises the steps of determining a first splitting point of a fault point in a target power grid after a fault occurring in the target power grid is removed; determining balance capability of a power supply station arranged behind the first splitting point in the target power grid; and determining a decomposition strategy of the power supply station arranged behind the first splitting point according to the balance capability so that a power supply protection strategy of the power supply station arranged behind the first splitting point is determined according to the decomposition strategy, wherein the power supply protection strategyis made according to a relay protection device, a low-voltage load reduction device and an automatic switching device. By the method, the technical problems of time-space matching relation and real-time running condition phase separation of an existing protection device and an automatic device in the prior art are solved.