A method and a device for adjusting a 3D model are disclosed. The method includes: fusing a 2D video and a 3D model of a target monitored area to generate a mesh model (S101); determining whether each set plane in the mesh model is even based on the location of a respective reference plane in the 3D model (S102); for each set plane that is uneven, referred to as a target set plane, selecting an uneven point in the target set plane as a mark point (S103), and generating a virtual plane based on the mark point and the reference plane corresponding to the target set plane (S104); and adding the virtual plane to the 3D model, and for the 2D video, saving the 3D model in which the virtual plane is added (S105). With the embodiments of the present application, operations for the uneven planes improve the effect of the fusion of a video and a 3D model. There is no need to modify a 3D scene model, which reduces the labor cost and time cost of modifying the 3D scene model.