The calculation accuracy of total supply capability（TSC）for power distribution network is investigated.Both the currently used model method and analytical method of TSC calculation for power distribution network as reported in literature are based on interconnections between substation transformers.Their TSC results failed to pass the N-1simulation test，which is a proof that there exist definite errors with these methods.A new model and its calculating method for TSC are proposed based on interconnections between feeders，which takes into account the contingencies of both substation transformers and feeders，plus an overall consideration of the network topology.The calculating method is capable of calculating the load of each feeder when the distribution system is operating at TSC.A case study is presented to compare the proposed method and the two typical methods available.The results of the N-1simulation show that the TSC result is on the boundary of N-1security，which means the proposed feeder-based TSC model is accurate.