A disk snapshot acquisition method, which is applied in a server comprising a memory allocated with a kernel space and a hard disk, comprises the steps of allocating all chunks having data stored as a disk volume in said hard disk; allocating a first portion and a second portion in said hard disk; establishing a snapshot pointer in said kernel space, said snapshot pointer pointing to a starting address of said first portion in said hard disk; and when original data in one of said chunks of said disk volume is to be modified, duplicating said original data to a chunk in said second portion as backup data, then modifying said original data into modified data, and storing a piece of mapping information comprising an address of said modified data and an address of said backup data corresponding to said modified data to a copy-on-write table in said first portion.