The present invention proposes a computer system and a method capable of performing integrity detection, comprising: a running mode unit which comprises an integrity detection boot variable to determine whether or not to initiate an integrity detection boot mode by judging said running mode unit; an EFI integrity detection unit (5), which is used for performing an integrity detection on EFI image codes in the integrity detection boot mode, and comprises an integrity metric value for being compared with an EFI integrity calculated value generated after the EFI integrity detection unit performs the integrity detection on the EFI image codes, to determine the integrity of the EFI image codes; an operating system integrity detection unit (6); and an integrity management unit. The present invention is based on the EFI BIOS to perform the integrity detection on the operating system during the pre-boot stage, having better reliability and security.