The Ag/Cu bimetallic sheets prepared by roll cladding at ambient temperature were diffusion annealed for different time at 750 degreesC. The dependence of microstructure and element distribution in the Ag/Cu interface region on the annealing time was investigated. There was an evident recrystallization with the coarsened grains in the interface region when the composite sheets were annealed only for 0.5 h, With prolonging the annealing time, the width of the Cu diffusion region in the Ag side increased because the migration of Cu atoms passing through the original interface into the Ag side was faster than the reverse migration of Ag atoms into the Cu side. A fine-grain area appeared in the Cu diffusion region in the Ag side, especially for the composite sheets annealed for a longer time and some Cu-rich particles precipitated along the grain boundaries in the fine-grain area.