A spaceborne sea ice edge detecting method is developed using the Global Navigation Satellite System reflectometry (GNSS-R). The difference of reflected signal delay map (DM) were observed in the satellite reflected signal of sea ice relative to those of sea water. Combined with specular reflection point location, it can be used to detect sea ice edge. An adaptive threshold algorithm is employed to process TDS-1 satellite data for the available DM. The curve of the DM derivatives with the specular reflection point position is obtained. Through comparing DM observablebased detection results with sea ice extent data analyzed by multisensory, the delay distance of the DM effective area, the peak of the correlation power, and the normalized mean square error can be used for sea ice edge detection. The method using GNSS-R is feasible to detect sea ice edge in spaceborne environment.