The effects of poly(dimethylsiloxane)(PDMS) film on the propagation of surface acoustic wave is studied. An interdigital transducer is fabricated on a 128°YX-LiNbO3 substrate for exciting surface acoustic wave, which is used to heat the paraffin oil microfluid on the PDMS film. The temperature of the paraffin oil microfluid is then measured for calculating the attenuation of surface acoustic wave. Results show that surface acoustic wave is attenuated by PDMS film on the piezoelectric substrate, and the value of the attenuation is increased with the thickness of PDMS film. The attenuation ratio is 23.3% and 36.0% respectively, when the thickness of PDMS film on the piezoelectric substrate is 100 μm and 150 μm.