The invention relates to a method for realizing starting of Linux operation system on a hard drive when the hard drive is inserted into the USB interface of PC, which is carried out by the steps of: building up a Linux operation system in a hard drive, entering the BIOS of PC, setting the start mode as USB-HDD or USB-ZIP, starting the system bootstrap routine, selecting the Linux edition, and downloading the Linux internal kernel and Initrd to the internal memory of PC from mobile hard drive, starting the internal kernel of Linux, initializing the system and loading task, entering the file system of Initrd, switching to the root file system of the mobile hard drive, detecting the hardware equipment and installing the drive program automatically and implementing the automatic configuration, starting the desk system, and after the user enters the user name and cipher, detecting and mounting the hard disk partition.