In order to evaluate the quality of the offshore magnetic data in the Earth Magnetic Anomaly Grid (2-arc-minute resolution)(EMAG2), the authors chose the aeromagnetic data at 1∶500 000 and 1∶1 000 000 scales of the southern section of the Kolbeinsey Ridge with a total area of 193 500 km² to compare and analyze. Based on the EMAG2 data, the authors obtained the EMAG2 (downward continuation 4 km) and the aeromagnetic anomaly (upward continuation 4 km) using the analytical continuation method. Then, the correlation coefficients between the aeromagnetic anomaly (upward continuation 4 km) and the EMAG2, and the aeromagnetic anomaly and the EMAG2 (downward continuation 4 km) were calculated by the correlation analysis method. Finally, through comprehensive analysis of the features of these correlation coefficients and differences, the quality of the magnetic data of the southern section of the Kolbeinsey Ridge was evaluated in the database EMAG2. The results showed that the EMAG2 integrated a large number of the airborne or offshore magnetic data. The quality of the offshore magnetic data is relatively high in the offshore areas with dense lines. However, the quality of the offshore magnetic data is relatively low if the EMAG2 data at 4 km altitude is converted to the anomaly data at sea level.