1. A computer-implemented image composition method for compositing sequential images, comprising: process A of: receiving a first image composition instruction from a user, by a receiving module having a processor, the first image composition instruction comprising an image identifier of a base image and information on a pre-specified modification area, wherein the image identifier of the base image indicating the base image selected from a plurality of sequential images; process B of: selecting a second image from the plurality of sequential images other than the base image, and if the selection fails, ending the image composition, otherwise, replacing the content of the pre-specified modification area in the base image with the content in a corresponding pre-specified modification area of the second image, and outputting the base image after the replacement; process C of: receiving a second operation instruction from a user, and if the second operation instruction is a non-ACK instruction, returning to the process B, but if the second operation instruction is a ACK instruction, saving the base image after the replacement.