Abstract: The argument about the cause of geological disaster(natural or man-made) induced by excavation unloading during the construction period is raised. A case study of the landslide occurred on the slope of an expressway in north China is conducted. The slope is a dip slope composed of the weak interbedded mica schist. Through the engineering geological survey and data analysis, it is concluded that the multiple weak interlayers which constitute the slope body and the strong precipitation encountered during the construction are the main natural reasons that affect the slope stability. Insufficient understanding of the complex geological conditions, and inadequate prevention and control measures during the investigation, design and construction process are the main man-made reasons. The weights of six parameters including natural and human factors are calculated using Analytic Hierarchy Process(AHP), Multi-factor interaction matrix method and Delphi method, and then the responsibility is divided. The results of this study are expected to provide some references for the selection factors of similar engineering and the division of responsibilities.