The c-axis oriented Er0.11Al0.89Nz films were prepared on sapphire substrates from a single target with Er metal ingots by RF reactive magnetron sputtering. After optimizing by the orthogonal design experiment, the thickness and surface rough ness of Er0.11Al0.89Nz film are 1.20 μm and 1.0 nm, respectively, and the optical permittivity of doping film increases from 4.19 to 4.29.The Er0.11Al0.89Nz/sapphire based SAW resonators has lower center frequency and Q value compared with the pure AlN, but the electromechanical coupling coefficient is up to 18%, 20% higher than that of AlNz/sapphire based SAW resonators. The crystal structure of thin film shows that the lattice constant ratio of c/a remains unchanged after Er doping AlN. However, the Er dopant will introduce ionic bonds to AlN, which soften the crystal structure, leads to a large electromechanical coupling coefficient.