A photo alignment process and a liquid crystal display using the same are provided. The photo alignment process includes the following steps. A photo alignment material layer is formed on a substrate. The photo alignment material layer is irradiated by a linearly polarized light. A surface of the photo alignment material layer is a first plane. A wave vector of the linearly polarized light is a K vector. A second plane is constructed from a normal vector of the first plane and the K vector. A polarization direction of the linearly polarized light is neither perpendicular nor parallel to the second plane.