One of the major problems comparing the old map, Daedongyojido, with modern maps in order to measure the spatial error of the map it a projection of the modern map selected. This study focuses on the map projection of Daedongyojido. Three different approaches are used: comparing the spatial pattern of Daedongyojido with maps of different projection, examining materials related to old maps and books which were written by Jeongho Kim directly or indirectly, and the data sets which were available at the mid nineteenth century and could be used for map production. A couple of map projections are possible to that of Daedongyojido, but TM(Transverse Mercator) projection is one of the closest projections.