The invention discloses an auxiliary power supply device, which comprises a rectifier module, a switch power supply module, an inverter power supply module, a control module and a switching control module; the rectifier module is used for rectifying input commercial power; the switch power supply module is connected with the rectifier module and is used for converting a direct current output by the rectifier module to a direct current with a preset voltage value; the inverter power supply module is connected with the rectifier module and is used for converting a direct current output by the rectifier module to an alternating current with a preset voltage value; the control module is used for controlling the switch power supply module and the inverter power supply module to run; and the switching control module is connected with the control module and is used for responding to operation of an operator to input a power supply switching control signal to the control module. According to the auxiliary power supply device, by combining the switch power supply module and the inverter power supply module in a same set of control system, selective output of power supplies in various specifications in one power supply equipment is realized, the need of a handcart type vacuum switch for the power supplies in various specifications in field when a characteristic test is carried out is met, the circuit structure of a vacuum switch characteristic test auxiliary power supply is simplified, the weight is lightened, and a field test is convenient.