More than half century ago, a high pressure carbon phase was first observed in single crystal graphite at room temperature, until now the structure of this high pressure carbon phase still remains unresolved and the main obstacle is the poor crystallinity of it. Here, with in-situ room temperature single crystle X-ray diffraction and Raman spectroscopy studies on single crystal graphite under compressed in diamond anvil, we discovered that above 14 GPa graphite crystal transformed to a three dimensional (3D) collapsed carbon phase with a hexagonal like symmetry. Accompanying with the phase transition, an strong anisotropic resistivity evolution along c axis and ab plane further reveals in collapsed carbon phase the free π electrons are two dimensionally (2D) localized in buckling basal graphene layers.