To investigate the SAW properties of GaN films on c-plane sapphire substrates, we carried out both the experimental measuring and theoretical calculation. The experimental characterization of SAW propagation properties was performed with a linear array of interdigital transducer (IDT) structures, while SAW velocities were calculated by matrix methods. HVPSAW mode with the propagation velocity over 10,000m/s and PSAW mode as well as GSAW could be observed in experimental determination. These results were verified by matching with the theoretical calculation.