According to the absorption of the near infrared (NIR) light by the liquid film, an optical sensor was designed to measure the disturbance wave frequency. This NIR sensor was designed with a vertically transmitted light path. Then by measuring the attenuation of the light intensity, the dynamic local film thickness was obtained. Using the power spectral density (PSD), the data of disturbance wave frequency were got. The results showed that the wave frequency increases with the increase of gas velocity and gas density. Based on the experimental data under different pressures of 0.3–0.9MPa, a calculation for the wave frequency was proposed. This calculation could achieve good fitting for both the current data and the available data, with MAE of 10.45% and 25.16%, separately.