The invention provides a standby power supply detection method and a standby power supply detection device. The standby power supply detection device comprises a first switch, a second switch, a constant current source, a bypass load and a controller; an input end of the first switch is coupled to an external power supply; an output end of the first switch is coupled to a standby power supply; when the first switch is switched on, the external power supply charges the standby power supply; an input end of the standby power supply is coupled to an input end of the second switch; an output end of the standby power supply is coupled to an input end of the external load; after the constant current source is connected with the bypass load in series, the constant current source is connected to two ends of the standby power supply in parallel; the controller further controls switch-on or switch-off of a path from the standby power supply to the constant current source; and the controller is also coupled to the output end of the standby power supply so as to acquire an output voltage of the standby power supply.