The invention discloses an AC charging automatic switching circuit for a DC system. The AC charging automatic switching circuit for the DC system comprises an AC input I, an AC input II, an air switch, an AC charging bus and two groups of inverter power supply modules, wherein each group of inverter power supply modules comprise more than one inverter power supply module; the AC charging bus is divided into two segments; two segments of AC charging buses I and II are connected through a contact of a parallel contactor KM3; the AC bus I is directly connected with one group of inverter power supply modules; and the AC bus II is directly connected with the other group of inverter power supply modules. Two paths of AC inputs are provided to the inverter power supply modules for working in an ''automatic manner''; if the switching circuit is abnormal, the condition that a normal AC input branch is provided to the corresponding inverter power supply modules for normally working can also be ensured even if one path of AC input is abnormal; and the condition that a DC bus voltage is not lost can be ensured, so that a DC storage battery is always in a charged state.