In this paper an optical configuration of a transflective liquid crystal (LC) cell driven by a horizontal electric field is proposed, which shows high contrast, high cellgap tolerance, and single gamma, simultaneously. The dark state of the reflective part is realized by a polarizer (0 degrees), a half-wave plate (15 degrees), LC layer (120 degrees), and a quarter-wave layer (-15 degrees), while a wide-band quarter-wave plate (45 degrees) and a polarizer (90 degrees) are added for the dark state of the transmissive part. Since the optic axis of the homogeneously aligned LC layer is set to be parallel to the polarization direction of the light passed through the half-wave plate, the dark state is rarely affected by the cellgap of the LC layer. Due to the different directions of the electric fields, LCs are rotated to 97.5 degrees for the bright state of the reflective part, but to 75 degrees for that of the transmissive part. With the proposed configuration, a high contrast single-gamma transflective display with high cellgap tolerance can be realized in a single-cellgap structure.