Sc-doped AlN films with (100) orientation have high surface acoustic wave velocity and excellent optical properties. Sc-doped AlN thin films based on flexible substrate were prepared by RF reactive magnetron sputtering at pressure levels ranging from 0.3 Pa to 1.5 Pa. The sputtering rate, crystal quality, and electric properties of the Sc-doped AlN films were investigated. The results show that pressure greatly influences the preparation of Sc-doped AlN thin films. Under low pressure, (002) oriented Sc-doped AlN film was prepared; with increasing pressure, the fraction of the (100) plane increased. Furthermore, the electrical properties were closely related to the crystal quality, achieving a maximum resistivity of 3.5 × 10 12 Ω · cm, a minimum leakage current of 0.65 × 10 −8 A, and a maximum piezoelectric response of 5.2 pC · N −1 .