1. A method for installing application software onto a virtual machine, comprising: mounting, by a processor, mirror data of the virtual machine where application software is to be installed, wherein the mirror data comprises at least an operating system file of the virtual machine and a user file, and mapping the mirror data as one virtual disk in a local file system; updating a registry file in the virtual disk according to registry change record data in an application software package of the application software, wherein the application software package comprises a file that is added or modified during an installation process, the registry change record data, and file change record data, and the registry change record data and the file change record data are obtained according to a difference between a host operating system environment before installation of the application software and a host operating system environment after the installation of the application software; and updating a file structure in the virtual disk according to the file change record data and the file in the application software package, thereby implementing installation of the application software in the virtual machine.