Abstract: The experimental research on cross flow pasting a circular cylinder near a plane boundary is conducted based on the particle image velocimetry(PIV)system. The experimental principle and devices are introduced. The problems about parameter's selection and particle's tracking are discussed. And the flow characteristics of the upstream of the cylinder are analyzed. Behind the cylinder,the dynamic process of the vortex formation,its development and extinction are displayed on the sub-critical Reynolds number range and gap-ratio is 0.5. The structure of the time-average and instantaneous flow field is compared. Finally,the characteristics of the vortex shedding in the wake are analyzed. Under the given experimental condition,the conclusion is drawn that the Strouhal number keeps the constant of 0.2.