Computer system and method used for accessing virtual machine

The invention provides a computer system and a method used for accessing a virtual machine. The computer system comprises a host operating system equipped with a host drive program and a virtual machine device; the virtual machine device comprises a virtual machine management program and a client operating system; when the host operating system needs to access the virtual machine device, at least one access instruction is sent to the virtual machine management program of the virtual machine device through the host drive program; the access instruction is received from the virtual machine management program by a client drive program of the client operating system of the virtual machine device; a client application program, a real hardware device and/or a virtual hardware device are access according to the requirement of the access instruction so as to generate an access result, and the access result is sent back to the host operating system.