Analytical signals estimated from total field magnetic anomalies in eastern China and adjacent seas are found to be more accurate in detecting locations, depths, and boundaries of magmatic bodies than original magnetic anomalies. The depth distributions of magmatic sources differ significantly between different tectonic blocks. The North China Craton shows high analytical signal amplitudes and large lateral extensions, but the detected magmatic sources are mostly deeply buried at depths up to 10 km or larger. This indicates strong magmatic activities in the lower to middle crust of the craton from tectonic reactivation. Due to tectonic uplifting and magmatic intrusions, the Sulu-Dabie Orogen has mainly shallowly buried magmatic bodies with depths smaller than 5 km. The Yangtze Block shows predominantly deeply buried magmatic sources, but unlike North China Craton, the magmatic activities in the Yangtze Block appear to be very weak and the calculated analytical signal amplitudes there are very small. The Cathaysia Block and its offshore northeastward extension is dominated by relatively isolated and shallow magmatic bodies (mostly <5 km) that are mainly caused by the subduction of the Paleo-Pacific Plate in the late Mesozoic. Depths of magmatic sources in the East China Sea correlate well with basement uplifts and depressions caused by Cenozoic continental margin rifting. The Ryukyu Archipelago corresponds with a very quiet magnetic zone and shows deeply buried magmatic sources, and these observations support the reasoning that the Ryukyu Archipelago itself is not the volcanic arc from the subduction of the Philippine Sea Plate but is composed of accretionary materials and/or continental blocks separated from the Eurasian Plate by opening of the Okinawa Trough. The true volcanic arc is represented by a volcanic belt slightly to the west of the Ryukyu Archipelago.