The invention discloses a method for expanding the capacity of a virtual disk, which includes the following steps: creating a virtual disk file according to a preset system image and a target disk capacity value contained in a received capacity expansion request; mounting the virtual disk file to a physical host, and generating a corresponding virtual disk; reading the partition information of thevirtual disk; deleting a to-be-expanded partition of the virtual disk, and creating a new partition according to the partition capacity value and the expansion value of the to-be-expanded partition;and reading the file system of the virtual disk, and expanding the capacity of the file system to make the file system adapt to the new partition. The method for expanding the capacity of a virtual disk is implemented based on a physical host, shortens the I/O path, and improves the I/O efficiency. Meanwhile, there is no need to start a virtual machine on a physical host in the capacity expansionprocess of a virtual disk, the capacity is expanded before the startup of the virtual machine, and the technological complexity and the coupling degree are reduced.