Thin CuInSe2 films were synthesized via selenizing Cu-In alloy-containing precursors The alloy nanoparticles with CuIn and Cu2In were obtained via chemical reduction in ethylene glycol Nanoparticles with a size around 40-60 nm were formed The thin monophasic chalcopyrite CuInSe2 film with large grains was formed at 450 degrees C Using the alloy nanoparticles for the coating process was demonstrated to be a potential way for preparing thin CuInSe2 films