Abstract: In the supertwisted nematic-liquid crystal display (STN-LCD), the director of liquid crystal is determined by the tilt angle θ and the twist angle φ. The ordinary differential equations and the boundary conditions satisfied by θ,φ and the electric potential U are obtained, based upon the continuum theory of liquid crystals. Solving two-point boundary problem of the ordinary differential equations by means of the relaxation method, dependence of the optical threshold voltage on the anchoring strength is calculated.