The thermal-stability and melting mechanism of the Ag nanocrystalline in the process of high-temperature relaxation are investigated with embedded atomic method and molecular dynamics simulations. The dynamic evolution of the crystalline’s morphology is revealed based on the analyses of mean square displacement and lifetime of the stability. It is concluded that there are obviously anisotropic behaviors in the process of high-temperature relaxation in the quasi-cubic nanocrystal which is cut along the inter-perpendicular facet of {110}, {211} and {111}. The thermal-stability decreases in the sequence of facet (111), facet (110), and facet (112). The lifetimes of the first outmost and the second outmost atoms in those three different facets are extremely short and show no evidently difference from each other. However considering the facets with the same crystal plane indices, the lifetimes are longer within the third atom layer and subtly increase with the increase of the number of atom layers. However, the lifetimes are distinctly different from each other among the three different facets within the third atom layer.