Abstract: Based on a vast amount of data of field investigations, this paper preliminarily studies the characteristics of surface rupture zone of the Lanzhou M 7.0 earthquake in 1125 and the activity features of the Zhuanglanghe fault since late Quaternary, and probes the structural background and macroseismic epicenter of the earthquake. Paleoearthquakes events along the Zhuanglanghe fault since Holocene period, etc. are discussed on the basis of analyzing the traces of paleoearthquakes.