An in-plane switching π-twisted liquid crystal device with fast response speed is proposed. Electric filed is applied in the plane of the substrates, unlike a conventional π-cell. Two quarter wavelength films are used to obtain black/white mode. The electro-optical characteristics and switching behavior of this mode are studied by using two-dimensional model. A good dark state is obtained when the electrode is black. Numerical results show that the proposed mode has excellent viewing angle and fast response speed.