Grain boundaries are the interfaces between differently oriented crystals of the same material. The underlying structures of grain boundary play a significant role in mechanical properties of polycrystalline materials. This influence becomes more significant when the grain size is reduced to ultrafine or nano size scale where the dislocation activities in the interior of grains lessen and mechanisms mediated by the grain boundary become dominant. This paper reviewed recent results in the atomistic simulation of the nanoscale behavior of grain boundary in face-centered cubic (fcc) metals. Three different simulation models were introduced to investigate the grain boundary behavior during plastic deformation, including three-dimensional (3D) nanocrystalline model, columnar nanocrystalline model and bicrystal model. The grain boundary was found to contribute to plastic deformation through the process of dislocation absorption, transmission or nucleation at boundary plane, as well as grain boundary accommodation mechanisms such as GB sliding and GB migration. These grain boundary mediated mechanisms were widely studied by the previous atomistic simulation works and were extensively reviewed here. Future challenges and directions in the computational study of grain boundary behaviors were also discussed.