Er/Yb co-doped Al2O3 films with variant Yb concentrations, which are controlled through adjusting the area ratio of Yb to Er in the surface of the target, are fabricated by radio-frequency (RF) reaction magnetron sputtering technique. The reliability of composition control of Er/Yb ratio in film prepapration and the influeme of Yb doping concentration on room temperature photoluminescence (PL) spectral intensity and distribution of Er/Yb co-doped Al2O3 films are mainly investigated. Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray analysis (EDX) are used to determine the composition of the films. It is shown that the concentration ratio of Yb to Er in the films accorded with the area ratio of Yb to Er in the surface of the target. The room temperature PL spectrum of the films after annealing at 1000 ℃ for 2 h shows that the PL intensity of Er3+ can be enhanced by Yb doping. The PL intensity and full width at half maximum (FWHM) reaches its maximum when the area ratio of Yb to Er reaches to 4∶1. The results of the research show that, as far as Al2O3 films are concerned, appropriate concentration of Yb/Er not only improves the luminescence efficiency of the films, but also enhances the channel bandwidth.