The invention discloses a picture segmentation method based on JPEG document flow. The method comprises the following steps: the step 1 in which the picture size, re-entry interval and sampling factor information can be acquired according to the JPEG coding theory and the data stream format thereof; the step 2 in which the picture segmentation number is calculated according to the JPEG picture size and read re-entry interval number; and the step 3 in which segmentation is performed on a JPEG picture according to the segmentation number, and segmentation reading is performed on the JPEG picture circularly. According to the method of the invention, the problem of size difference and especially problems of large memory usage, large time consumption and low efficiency with oversized pictures can be effectively solved, and advantages of less memory usage and stability can be realized.