In this paper, the relationship between Love wave velocity and the polymer film thickness was studied by combination of test and numerical calculation. The Love wave device consists of two interdigital transducers (IDTs), an ST-90°X quartz substrate, and a polyvinyl alcohol (PVA) layer. A network analyzer was used to measure the operation frequency and insertion loss of the sensor along with the change of film thickness at the relative humidity of 35%. Based on the experimental data, the relationship between Love wave velocity and the polymer film thickness was calculated and the propagation characteristic of Love wave was verified. When PVS film thickness was increased from 0 to 5% of the wavelength, the Love wave velocity decreased from ~4 992 m/s to 4 840 m/s, which is consistent with the calculated results.