Cuprous oxide (Cu₂O) thin films were deposited by radio frequency(RF )magnetron sputtering,using a metallic copper in O_2and Ar mixture atmosphere,and the as-deposited thin fi lms were then annealed by a rapid thermal annealing (RTA) in N_2atmosphere. Effects of substrate temperatures an d annealing temperatures on growth behavior,crystalline structure,surface morphology and optical properties of as -deposited and annealed Cu₂O thin films are investigated.The results show that the thin films deposited at substr ate temperatures below 300℃ are amorphous.The RTA process has obvious influence on the crystallinity of the thin films,but the crystalline phase of the thin films has no change after annealing in N_2atmosphere.The thin films have strong absorbance for wavelengths bel ow 650nm,and the absorption intensity of thin films increases with annealing temperature increasing.The two optical abs orption processes for wavelengths below 400nm are probed,and these behaviors might arise from the inter-band ( IB) absorption,resulting from defect states in thin films,which indicates that the RTA of thin films could no t decrease or eliminate defect states during thin films deposition.Moreover,th e RTA process affects the optical band gap (E_g) of th in films,and Eg of the thin film annealed at 600℃ is enhanced by about 0.26eV compared with that of as-deposited thin film.