The invention provides a method and device for directionally widening electronic map road segments. The method includes the steps that all road segment sets of a target road network are acquired, wherein each road segment set psi comprises multiple road segments connected topologically; an inner point ordered set Ppsi of each psi is extracted, a road segment curve of each psi is directionally widened in the up direction according to the inner point ordered set Ppsi, and an inner point ordered set EPpsi, d of a parallel curve of each road segment curve is acquired; whether self-intersection occurs to the parallel curve of each road segment curve or not is judged according to EPpsi, d, if yes, a self-intersection region of each parallel curve is detected, and all inner points in the self-intersecting region in EPpsi, d are deleted; the deleted road segments generated after the inner points are deleted are restored according to the segmented corresponding relationship between the parallel curves and the corresponding road segment curves. The electronic map road segments can be directionally widened, the parallel curves, with designated width, of the road segments are generated, the segmented corresponding relationship between the parallel curves and the original road segments is reserved, road condition information is precisely displayed, actual requirements on self-intersection region processing are met, the calculation complexity is reduced, and the calculation efficiency is improved.