Abstract: This paper discusses the method by which the regional anomaly can be abstracted.On the basis of making a series of upward continuation of the aeromagnetic data from Beijing-Tianjin and surrounding areas, it is proposed that the regional anomaly can be divided into two parts: the upper one and the lower one corresponding to the upper and lower crustal magnetic layers, respectively. According to the Pre-cambrian metamor-phic basement the study region can tectonically be divided into six blocks. Moreover, from the lower regional magnetic anomaly it can be derived that the lower magnetic layer may be largely affected by the thermal events related to the Mesozoic and Cenozoic magmatism. This paper also discusses the deep regional anomaly, presumably resulting from the rise of the Moho surface.