In the present paper, the evolution process of the mixing layer manipulated by a vortex ring was studied using a novel experimental technique. Mixing layers were generated downstream from a splitter plate towed in a straight long channel. The vortex ring was made to collided with the mixing layer large-scale structures in the transitional region. The interactions between the mixing layer and the vortex ring were investigated by means of the flow visualization and the flying hot-wire technique associated with the collision. The topology of the vortices effective for pairings of the mixing layer is presented in this paper. The experimental results reveal that the vortex ring deforms the mixing layer vortices and causes the deformed vortices to merge sooner than they do in the case forced by the subharmonic instability modes.