A computer has a plurality of sleeping modes to be switch directly. The power supply assemblies provide a plurality of power supplies to elements in the computer. The storage module is used to store executing data corresponding to each sleeping mode. The power management module is used to set the number of the power supply assemblies which need to be switched on in each sleeping mode. The control module determines the sleeping mode which is switched to according to a received trigger event and sends a first switching signal to the storage module to make the storage module store the executing data and a second switching signal to the power management module to make the power management module set the number of the power supply assemblies and switches the sleeping mode of the computer directly.