The embodiment of the invention discloses a method and a device for copying an image file. The method comprises the following steps of when the image file of a production center is copied to a data backup center, obtaining the target position information of a copied data block of the current image file; when a write request on the image file is received, and the number corresponding to the starting position of the write request is greater than the number corresponding to the target position, directly executing the write request; when the number corresponding to the starting position of the write request is smaller than the number corresponding to the target position, executing the write request, and recording the write request into a pre-established write request log; when the copying of the image file of the production center to the data backup center is completed, transmitting the data of the write request log to the data backup center, and replaying, so as to form an effective image snapshot. The method disclosed by the embodiment has the advantages that the influence to the I/O (input/output) request operation of an upper layer is low in the image file copying process, the log copying operation is reduced by one half, and the copying efficiency of the image file is improved.