In this paper, a description of the process by which two kinds of surfactants with relative long or short alkyl chains are introduced onto the surface of Ag nanocrystals, which contribute to the formation of tunable and anisotropic "covalent bonds" between two Ag nanocrystals, is given. By altering the lengths of the short alkyl chains, the sizes and structures of the as-obtained supercrystals as well as the exposed crystal planes of the interior nanocrystals can be tuned. This strategy may further enrich the "chemical bond" categories of artificial atoms and serve as the base for the discovery of more functional superstructures.