In this paper,the authors systematically analyzed and studied the geophysical field and characteristics of the basement structure of Tianjin by using gravitational,magnetic and electric data.Some conclusions have been reached:the analysis of the gravitational,magnetic and electric field could satisfactorily recover the tectonic framework of the study area,the regional geophysical field is the reflection of the Archean crystalline basement,the change of the local field has close relationship with the pre-Mesozoic folded basement,the pre-Mesozoic basement shows a characteristic of fault block combination cut by the fault,and there are magnetic volcanic rocks distributed along the huge fault.On the basis of the delineation of the master fault system,the authors divided the study area into four tectonic units:Malanyu anticline,Jizhong depression,Changxian rise and Huanghua depression;using the gravity and magnetic anomaly,the authors delineated the distribution of local structures and magnetic geological bodies.The results obtained by the authors provide basic geophysical data for the study of the regional crustal stability and the evaluation of mineral resources.