A light guide panel and a back light unit having the same are provided. The light guide panel includes an isotropic layer and an anisotropic layer. The isotropic layer includes an incident light surface, a transmission surface, and a polarization recycling unit, disposed opposite the transmission surface, which changes a polarization direction of light. The isotropic layer has a first refractive index. The anisotropic layer is formed on the transmission surface and includes a selectively transmitting and reflecting surface opposite the transmission surface, which reflects a first portion of incident light and transmits a second portion of incident light. The anisotropic layer has a first refractive index, identical to the first refractive index of the isotropic layer, with respect to light having a first polarization and has a second refractive index, different from the first refractive index with respect to light having a second polarization.