Abstract: In this paper, a linear barotropic model is used to investigate the structural characteristics and generation mechanism of atmospheric low-frequency variability (LFV) principal mode, with the basic flow being observed during Northern Hemisphere winter. After applying statistical analyses to the model's solutions, it is demonstrated -that the low-frequency principal mode is accompanied by the inherent preferred model patterns and forced excitation regions, and the dominant mechanisms responsible for generating LFV principal mode are related with the zonal asymmetries in the basic flow and the related barotropic energy conversion processes.