Mark point(Donghaksan) of Korean geodetic datum in Suwon could not be intervisible because of the development of the surroundings, so we were in a situation that we should establish new mark point and decide azimuth of the new mark point. Getting out of the intervisibility between control stations, refraction error and effect of illumination in urban area, our research team decided new azimuth of Suwon Geodetic Datum by GPS surveying for accuracy and economical efficiency. First we corrected and supplemented the specification on the decision of azimuth in accordance with our situation based on the study of foreign studies by using GPS, and we determined and analyzed the accuracy of the new azimuth through organizing and observing the GPS network.