The invention discloses high-stability power supply device for a power system. The power supply device comprises a communication function module, and further comprises an AC 220V power supply module,a DC 220V power supply module and a power supply mutual switching module; the AC 220V power supply module and the DC 220V power supply module are connected with the power supply mutual switching module; the power supply mutual switching module is connected with a power supply conversion module; the power supply conversion module is connected with the communication function module; the AC220V powersupply module is connected with a first anti-surge module; the DC220V power supply module is connected with a second anti-surge module; the power supply device further comprises a control module; thecontrol module is connected with the AC 220V power supply module and the DC 220V power supply module, comprises a monitoring module and is connected with an alarm module; and the AC 220V power supplymodule and the DC 220V power supply module are connected with an indicating lamp. The power supply device is suitable for the original AC220V and DC220V power supplies of the transformer substation,a communication direct-current power supply does not need to be additionally established or intermediate conversion equipment does not need to be used for intervention, the cost is reduced, the stability of the power supply is improved, and normal work of communication equipment and normal transmission of uplink and downlink data are ensured.