Abstract: The effects of porous media on the flow around a circular cylinder were investigated experimentally using the synchronous measurement of hot-wire anemometry, smoke-wire visualization and particle image velocimetry (PIV). The frequency characteristics, time-average and instantaneous flow field of the wake were measured and analyzed for improving understanding on the mechanism of flow modification caused by porous layer coating. The results show that the large-scale vortex shedding structure is effectively inhibited with porous layer coating and the Strouhal number of vortex shedding is 0.162 for the porous one which is smaller than 0.182 for the bare one.Additionally, the peak power spectral density of velocity is decreased in the near wake (x/D≤1.5), while increased in the far wake (x/D>1.5) and the position of obvious vortex shedding shifts downstream.Porous media attenuate the velocity of the wake region and widen the wake, leading to the weaker interaction between the two slenderer shear layers and slower rate of vortex interaction. Meanwhile, the porous media significantly eliminate the velocity fluctuations in the streamwise and spanwise, especially in the centerline as well as the Reynolds stress in the wake. The positions of peak value of Reynolds stress and time-averaged vorticity are more far away from the cylinder, so that the porous media weaken the instability of the shear layer and increase the vortex formation length.