Abstract: Transonic flows have presented an enduring challenge to experimental research due to their intricate and unsteady flow characteristics. This study investigated the megahertz-frequency Particle Image Velocimetry（MHz–PIV）technique to enhance the resolution of small time-scale flows under the transonic flow conditions. During the measurement, five high-speed cameras alternately and quickly captured images of the same measurement area, and thus obtained ultra-high time resolution particle image data. By employing image processing techniques optical distortion correction and identification of the common area were achieved. The application of the ensemble correlation algorithm, coupled with spectral analysis of the compressible turbulent flow field based on the velocity field, contributed to a comprehensive analysis. The experiment validated the high-frequency sampling capability of MHz–PIV, which significantly reduces the technology’s dependence on camera performance. This approach offers a refined measurement technique with high spatiotemporal resolution for transonic experiments.