Abstract: Although the flow around a circular cylinder has been investigated for a long time, some problems such as the mechanism of Karman vortex and the reduction of vorticity in the vortex street remain to be solved.The present paper gives some results associated with the characteristics in the "dead-water regin" which are experimentally investigated by means of hot film, hot wire and sublayer fence.The results show that the flow structure of the "dead-water regin" at high Reynolds numbers is similar to that at low Reynolds numbers. Finally, the mechanism of the vortex street formation is briefly discussed.