A method and an apparatus for determining the distributed power supply capacity to be accessed by a feed line of a power distribution network, and a storage medium, the method comprising: determining feed line loss on the basis of load information of power distribution network feed line access nodes and circuit parameters; on the basis of the feed line loss, determining three-phase voltage change values of the feed line circuit; using a single phase having the greatest voltage change amongst the voltage change values, determining a maximum active power for distributed power supply access under voltage constraints; comparing the current of the feed line corresponding to the maximum active power with a circuit current limit, and determining the distributed power supply capacity to be accessed by the feed line; the apparatus comprises a feed line information collection unit, a voltage drop unit, a quantitative calculation unit, and a results analysis unit. The present method can be used for dispatching operation control of a distributed power supply in a power grid, and can ensure safe access to the distributed power supply and safe operation of the power grid, improving the access capacity of the power distribution network to the distributed power supply.