CuCr _0.93 Mg _0.07 O ₂ thin films with improved optoelectronic properties were deposited by reactive magnetron sputtering on fused quartz substrates. The influence of annealing temperature under vacuum on optoelectronic properties of the films was investigated. The amorphous films annealed under vacuum at temperatures higher than 923 K are single-phased delafossite structure, while impurity phases like CuCr ₂ O ₄ that affect the optoelectronic properties of the films are detected below 873 K. c -axis orientation is observed for CuCr _0.93 Mg _0.07 O ₂ layers and the annealing temperature window in which the films are single-phased delafossite is much larger with Mg doping (923 K → 1073 K) than that for undoped films (~953 K). The optical and electrical behaviours of the films are enhanced by Mg substitution and their direct band gap energy of about 3.12–3.14 eV is measured. The film possesses the optimum properties after annealing under vacuum at about 1023 K; its average transmittance in the visible region can reach 54.23% while the film’s conductivity is about 0.27 S cm ⁻¹ .