Silver nanocrystal arrays had attracted much attention due to the unique plasmonic effect of their ordered nanostructure and the synergy among adjacent nanocrystals. Conventional preparation methods had several limitations, such as high cost, harsh preparation conditions, and complicated influencing factors, which could not be employed to fabricate the nanocrystal arrays in highly controlled fashion. To solve these issues, we reported ordered arrays of different Ag nanocrystals with precise control prepared by utilizing amphiphilic star-like poly(4-vinylpyridine)-block-polystyrene diblock copolymers as nanoreactors synthesized by sequential atom transfer radical polymerization. Moreover, this unimolecular nanoreactor method based on star-like copolymers with stable and predesigned nanostructures was proved to be a universal approach to prepare other nanocrystal arrays. This strategy had low cost, simple process flow, wide applicability, and structural stability that could fabricate nanocrystal array with precise control and continuously prepare more complex nanostructure units in a large scale to meet different functions and applications.