Based on the new Bouguer gravity and magnetic data of the East China Sea, the authors analyzed the characteristics of gravity and magnetic anomalies as well as their geological significance. The Bouguer gravity anomalies change differently from 160 to 460 mGal and some lower gravity anomalies appear in the positive anomaly background field. The magnetic anomalies change differently from -200 to +500 nT and the main trend of both Bouguer gravity and magnetic anomalies are in NE direction. The magnetic basement was calculated and the features of the basement and the geology were analyzed too. The magnetic basement depth changes from 4 to 12 km in different areas. There are Mesozoic strata in the East China Sea according to the studies in combination with the experience obtained by previous researchers.