A system for operating system recovery is proposed and includes a data storage device having a first partition, a second partition and a third partition including bootable files, and a BIOS (basic input/output system) having a recovery function. When the recovery entry is accessed, the BIOS is enabled to boot the computer system to the third partition. After the computer system is booted, an OS image file in the second partition is unpacked into an integral copy of the operating system. The integral copy of operating system and a patch file in the second partition are copied to the first partition. Then, the third partition is set hidden and inactive, and the first partition is set active, and the computer system is rebooted to the first partition. The patch file is executed to patch the operating system in the first partition after the computer system is rebooted to the first partition.