In South China which lies in low latitudes,there are large quantities of granites and volcanic rocks,whose magnetic fields are different from those in other areas.This paper applied 3-D analytical signal technique to the treatment of aeromagnetic anomalies in South China so as to probe into the application effects of analytical signal technique in areas with different geological settings.It divided the South China magnetic fields on the basis of intensities of analytical signals and,in combination with the achievements in seismic and isotopic geochemical studies of South China granites,investigated the deep geological backgrounds for the division of magnetic fields.