Abstract: Liaodong Bay is a Cenozoic rift basin in the Bohai Sea developed along the Tanlu fault. The distribution of fault system and the characters of basement have played critical roles in the performance of regional tectonics. This paper is devoted to the gravity and magnetic anomalies in Liaodong Bay based on previous tectonic researches, petrophysical properties and the newly acquired gravity and magnetic data from the various basic marine geological survey programs in China. There we made detailed description and comparative analysis of gravity and magnetic anomalies. In addition, regional tectonics of the study area are analyzed and interpreted. It is clearly noticed that the tectonic pattern of "east-west zonation" in Liaodong Bay Depression the difference of regional tectonic patterns vary with time from place to place. Together with the changes in distribution of main faults and magmatic rocks, the distribution of the new Archean curst basement in Liaodong Bay and its adjacent seas are also discussed.