The invention relates to an alternating current and direct current hybrid power supply system and method. The system comprises current transformers C1, C2, C3, C4 and C5, diodes D1, D2 and D3, intelligent control switches S1, S2 and S3 and a direct current bus. A principle of prioritizing usage of a local DG is adopted, and a self-adaptive power control strategy based on direct current bus voltage signals is employed; the intelligent control switches S1, S2 and S3 for a three-phase alternating current power grid, the local DG and a local energy storage component are automatically controlled according to a state of the direct current bus voltage signals; supply and demand power balance between the three-phase alternating current power grid, the local DG as well as the local energy storage component and electricity consumption of loads can be effectively regulated and controlled. The method is well compatible with traditional alternating current systems; problems of alternating current stability, voltage and frequency synchronization, reactive power and the like caused by the local DG being connected to a power grid in an alternating current form can be prevented; continuous and high-reliability power supply for local loads can be realized; influence exerted on user side electric energy quality can be reduced, local DG energy utilization efficiency can be improved, and an environment friendliness property is fulfilled.