The invention provides a single board, a backboard type switch and a method for connecting a power supply. The single board comprises a power supply monitoring module and a CPLD (Complex ProgrammableLogic Device). The power supply monitoring module and the CPLD can be used for controlling the connection condition of one or more power supplies and the single board according to the power supply requirements of the single board. The technical scheme is adopted. Two modules are used for alternately controlling the power-on and power-off of the single board; single board for multiple power supplies, power-on is kept in the upgrading process of the single-board power supply logic. The other module controls the power supply to be powered on and off, so that the service is not interrupted in theupgrading process. The problem of single power-on and power-off control process of the controllable single board in the related technology is solved. The two modules can alternately rest or execute operations such as upgrading and the like.