A method for switching an operating system, OS, adapted to an electronic apparatus having a processor, a system memory (130, 500), and a memory unit, the method comprising: when the electronic apparatus switches to a first OS, declaring that a first segment (221, 521) in the system memory (130, 500) is in a usable state and a second segment (223, 523) in the system memory (130, 500) is in a reserved state by using a first resource description table, so that the first OS is in a working state in the first segment (221, 521) and a second OS is in a power-saving state in the second segment (223, 523) and the electronic apparatus is operable by a user under the first OS; and when the electronic apparatus switches to the second OS, declaring that the second segment (223, 523) is in the usable state and the first segment (221, 521) is in the reserved state by using a second resource description table, so that the second OS is in the working state in the second segment (223, 523) and the first OS is in a power-saving state in the first segment (221, 521); wherein before the electronic apparatus switches to the first OS or the second OS, the method further comprises: when the electronic apparatus is turned on, generating (S305, S405) the first resource description table by a system firmware in the memory unit to declare that the first segment (221, 521) is in the usable state and the second segment (223, 523) is in the reserved state, and starting the first OS to work in the first segment (221, 521); receiving (S310, S409) a switching signal; and after the step of receiving (S310, S409) the switching signal, generating (S315, S419) the second resource table by the system firmware in the memory unit to declare that the second segment (223, 523) is in the usable state and the first segment (221, 521) is in the reserved state, and starting the second OS to work in the second segment (223, 523) and wherein the first OS is in the power-saving state in the first segment (221, 521). when the electronic apparatus switches to a first OS, declaring that a first segment (221, 521) in the system memory (130, 500) is in a usable state and a second segment (223, 523) in the system memory (130, 500) is in a reserved state by using a first resource description table, so that the first OS is in a working state in the first segment (221, 521) and a second OS is in a power-saving state in the second segment (223, 523) and the electronic apparatus is operable by a user under the first OS; and when the electronic apparatus switches to the second OS, declaring that the second segment (223, 523) is in the usable state and the first segment (221, 521) is in the reserved state by using a second resource description table, so that the second OS is in the working state in the second segment (223, 523) and the first OS is in a power-saving state in the first segment (221, 521); wherein before the electronic apparatus switches to the first OS or the second OS, the method further comprises: when the electronic apparatus is turned on, generating (S305, S405) the first resource description table by a system firmware in the memory unit to declare that the first segment (221, 521) is in the usable state and the second segment (223, 523) is in the reserved state, and starting the first OS to work in the first segment (221, 521); receiving (S310, S409) a switching signal; and after the step of receiving (S310, S409) the switching signal, generating (S315, S419) the second resource table by the system firmware in the memory unit to declare that the second segment (223, 523) is in the usable state and the first segment (221, 521) is in the reserved state, and starting the second OS to work in the second segment (223, 523) and wherein the first OS is in the power-saving state in the first segment (221, 521). when the electronic apparatus is turned on, generating (S305, S405) the first resource description table by a system firmware in the memory unit to declare that the first segment (221, 521) is in the usable state and the second segment (223, 523) is in the reserved state, and starting the first OS to work in the first segment (221, 521); receiving (S310, S409) a switching signal; and after the step of receiving (S310, S409) the switching signal, generating (S315, S419) the second resource table by the system firmware in the memory unit to declare that the second segment (223, 523) is in the usable state and the first segment (221, 521) is in the reserved state, and starting the second OS to work in the second segment (223, 523) and wherein the first OS is in the power-saving state in the first segment (221, 521).