Abstract: The airborne radar may affected by sea clutter or ground clutter when detecting targets on the sea surface. Due to the strong ground clutter, a lot of land targets will be detected, severely degrading the radar’s detection performance of sea surface target. In this paper, a sea target detection algorithm for airborne radar based on map information is proposed. The proposed algorithm first calculate the longitude and latitude information of the area, which the radar antenna beam illuminates, by using the carrier aircraft attitude data provided by inertial navigation system. Then search the sea-land information in the map data according to the longitude and latitude to realize the sea-land segmentation and realize the sea land detection. The proposed method is experimentally validated using real X-band radar detection experiment data, indicating that this method can recognize the target’s sea-land position exactly and help select or eliminate targets as demanded, significantly improve the radar’s detection performance.