Two-phase thin solid films consisted of Au nanoparticles imbedded in an amorphous matrix were prepared via a series of galvanic replacement reactions between chloroauric acid solution and reducing metals. The Au nanoparticles were in situ crystallized from the amorphous films rather than precipitated from solution directly. Amorphous films with partly crystallized Au nanoparticles only existed stably in dilute chloroauric acid solution. The higher concentration of chloroauric acid evidently promoted the strain-induced crystallization process and accelerated the crystallization of amorphous films into Au nanoparticles with many stacking faults, twins and dislocations. The coexistence of amorphous and crystalline Au nanoparticles makes it possible to synthesize two-phase nanostructured films.