Abstract: To improve the element uniformity of doped films, a method for preparing doped films by combined target co-sputtering was designed based on magnetron sputtering technology and used to prepare Al doped CdSe films.The homogeneous Al doped CdSe films were successfully obtained.The results show that the prepared films are Se-rich with an obvious (111)preferred orientation.The square resistance of CdSe film doped with Al increases from 5.2 kΩ/□to 544.5 kΩ/□, and the square resistance of the film decreases with the increase of Al content.When the Al plates on CdSe target are set to 6 pieces, the square resistance of the Al doped CdSe film is 7.7 kΩ/□, and the type of film changes from p-type to n-type.The doped films show electrical conductivities of 192.4 mΩ·cm(undoped), 2.01×10⁴ mΩ·cm(one Al plate on CdSe target), 506.9 mΩ·cm (two Al plates on CdSe target), 384.8 mΩ·cm (four Al plates on CdSe target)and 284.9 mΩ·cm (six Al plates on CdSe target), respectively.The band gap E_g of the doped film from the reflectance spectra measurement samples are 1.82 eV(undoped), 1.97 eV (one Al plate on CdSe target), 1.75 eV (two Al plates on CdSe target), 1.78 eV (four Al plates on CdSe target)and 1.82 eV(six Al plates on CdSe target), respectively.