Isothermal grain growth behaviors, including the effect of temperature and mean grain size, of nanocrystalline Ag are investigated using the molecular dynamics simulations with an analytical embedded atom potential. The atomistic simulations provide a level of atomic details on microscopic mechanism and process of grain growth that still remains inaccessible to experiments. The small grain size and high temperature accelerate the grain growth, it is the same as the conventional polycrystalline materials. The grain growth processes of nanocrystalline Ag are well characterized by a power-law growth curve, followed by a linear relaxation stage. Beside grain boundary migration and grain rotation mechanisms, the dislocations(or stacking faults)serve as the intermediate role in the grain growth process.