The present application relates to a method and device for segmenting lines in a line chart. The device converts a line chart in which N legends are detected from an RGB color model to an LAB space model to obtain an LAB value of each legend in the line chart and an LAB value of each pixel in the line chart respectively; performs Euclidean distance calculation on the LAB value of each legend and the LAB value of each pixel in the line chart to generate N color difference distribution maps, one legend corresponding to one color difference distribution map; and finds out the minimum in each color difference distribution map, setting a segmentation threshold with reference to the minimum, and segmenting a rough line corresponding to the color difference distribution map in the color difference distribution map according to the segmentation threshold.