The present invention discloses a passive grid-connected-to-off-network switching control method based on single three-phase multiple microgrids. Aiming at the influence of the passive off network on the multiple microgrids, a three-phase (PQ) energy storage regulation module and a single microgrid connection line power regulation module are established. The presetting three-phase energy storage after passive off network is arranged as a main power supply and is switched to a VF mode. The three-phase (PQ) energy storage regulation module is configured to reduce the three-phase main power supply power. Based on the three-phase unbalance constraint, the single microgrid connection line power regulation module is configured to limit the output of the single-phase photovoltaic to allow the multiple microgrids after off network to keep three-phase current balance. The passive grid-connected-to-off-network switching control method based on single three-phase multiple microgrids is simple and practical and can realize the seamless switching of the passive off network of the multiple microgrids through switching the three-phase main energy storage control mode and coordinating the three-phase (PQ) energy storage output and the limitation of the output of the single-phase photovoltaic. The passive grid-connected-to-off-network switching control method based on single three-phase multiple microgrids is provided to reduce the impact of the passive grid-connected-to-off-network process on the multiple microgrids and ensure the power supply reliability of the important load in the multiple mircogrids.