The crystal structure, crystallite morphology, film composition and absorption properties were investigated for the pyrite films sulfurated from iron films. The pyrite particles nucleate mainly from the transitional phases of iron sulfides formed in the films during 673K sulfurating while the pyrite particles nucleate directly from the iron bisulfides formed in the films during 773K sulfurating. There are higher sulfur contents and more obvious grain propagation in the film sulfurated at 773K than in that sulfurated at 673K. With prolonging sulfuration time at 673K, the optical absorption edge tends to increase and approaches to the ideal value as sulfurated over 20h. Low absorption edges exist in the films sulfurated at 773K.