Scandium aluminum nitride alloy(ScAlN) thin films were prepared on (0001) sapphire substrates by DC reactive magnetron sputtering with a scandium aluminum alloy (Sc0.06Al0.94) target.The crystal orientation and surface morphology were detected by XRD and AFM,respectively. The piezoelectric properties were analyzed by a piezoelectric response force microscopy(PFM).The results showed that the sputtering pressure appeared to be important to influence the crystal quality and piezoelectric response of ScAlN films.With the sputtering pressure increasing from 0.3 Pa to 0.7 Pa,the crystal orientation and surface morphology of ScAlN films firstly improved and then got worse.Meanwhile, the piezoelectric response of the films performed a similar variation. Finally, highly caxis ScAlN films could be obtained with a a sputtering pressure of 0.5 Pa,and the FWHM value of the rocking curve, the RMS roughness and piezoelectric constant d33 were 2.6°, 2.650 nm and 8.1 pC/N,respectively.