Abstract: A virtual machine backup method, performed by a first host, includes: capturing a request to write data from a virtual machine to a hard disk image file, wherein the request includes written data and input and output location information, copying the written data to a temporary storage area, calculating a first key of the written data, storing the first key, the input and output location information into a first resource location structure, pausing an operation of the virtual machine and generating a second resource location structure according to the first resource location structure, the first key and a second key, and outputting a backup data set to a second host according to the second resource location structure, wherein the backup data set includes the second resource location structure and only one of existing data and the written data when the first key and the second key are the same.