The coherent wake structures behind a spinning cylinder placed in a uniform flow were experimentally investigated by means of phase averaging technique. With a fixed cylinder Reynolds number (Re=6,600), the conditionally sampled velocity vectors were obtained at a section of 3.0 and 10 diameters behind the cylinder for the range of spin parameter S(the ratio of the peripheral velocity to that of the uniform flow) 0 to 2. Spectral analysis and vorticity contours of the velocity data show that up to S=1.2, a Karman vortex street exists within the wake, however, the coherent structures become obscure and their vorticity strength decreases as S increase. Beyond S=1.2, a distinct vortex shedding frequency no longer exists, furthermore coherent structures disappear when S is over 1.6.