A polyphase power dispatching system and a polyphase power dispatching method are provided. The polyphase power dispatching system includes an electric meter, a single-phase electricity storage module, a switch and a control circuit. The electric meter can measure transmission statuses of power transmission lines of a polyphase power line group. The common terminal of the switch is connected to the single-phase electricity storage module. The selection terminals of the switch are connected to the power transmission lines in a one-to-one manner. The control circuit is connected to the electric meter and the switch. The control circuit can correspondingly control the switch based on the transmission status of each power transmission line, so that the switch selectively connects the single-phase electricity storage module to one of the power transmission lines.