Real walking provides higher immersive presence for virtual reality (VR) applications than other locomotive methods such as walking-in-place and external control gadgets. Mapping based methods are effective for real walking in small physical spaces while exploring large virtual scenes. However, the existing methods for computing real walking maps either suffer from poor quality due to distortion, or require input to be a set of narrow pathways, which prevents users from walking freely in open scenes. In this paper, we propose a conformal mapping based methods for large-scale open scenes. The main process is as follows: first, some points are specified to allow the map of virtual scenes to circle around. We need also remove a small part around these points from the map. Then, a conformal mapping is built that make the mapping result circle around the points. The number of circles can also be specified by people. Finally, an optimization for isometric energy with the conformal mapping as initialization is adopted to further reduce the distortion throughout the map. This paper provides a high quality mapping method for large-scale open scenes with simple conformal mappings. The results of experiment show that our method can generate an effective mapping from large-scale open scenes to small physical spaces with low distortion.