Abstract: Debris flow is one of the main sudden geological hazards in the mountainous areas of Beijing. The development scale of debris flow is mostly small and medium-sized, but it is really dangerous. Therefore, it is necessary to carry out professional monitoring. Scientific selection of monitoring objects, reasonable selection of monitoring methods, types of monitoring equipment and reliable installation position, and clear monitoring technical requirements are the keys for debris flow monitoring and early warning. Based on the work practice of Phase I and Phase II of Beijing sudden geological hazards monitoring and early warning system, the authors in this paper summarized the contents of debris flow monitoring object selection, monitoring methods and equipment, methods and technical requirements for determining monitoring points, through the analysis of characteristics of debris flow in the mountainous areas of Beijing. Besides, the rationality of the above principles, methods and techniques is verified by taking the professional monitoring practice of Yinziyu debris flow in Xiaolianghougou as an example. The Relevant work can provide ideas and reference for early point selection of debris flow monitoring and warning.