In VR, how to map large-scale virtual space to small real space is a challenging problem. We propose a novel steering algorithm for the redirected walking(RDW) technique to direct users away from the boundary of the tracking area. When the user arbitrarily specifies the start and end points of the roaming, our system will generate a navigation path based on Voronoi automatically. During the navigation, we interactively and imperceptibly rotate the VE to make the user walking along arcs while thinking she is walking straightly. When the user is approaching the boundary, we hierarchically adjust the redirection gains to make the user turn away to avoid the reset procedure. To validate our algorithm, we conduct live-user comparison experiments with S2C method in a small tracking area using indoor(highly-constructed Maze) and open(long-straight Road) scenes which can be up to three orders of magnitude larger than the tracking area. The results indicate that our algorithm can effectively speed up and smooth the navigation, reduce collisions and perceptual distortion, show the potential to direct multiple users simultaneously, and be particularly suitable for individuals and small business users who cannot provide a large physical space.