The problem of optimal reliable guaranteed cost control with regional poles constraints is investigated for a class of uncertain discrete - time systems subject to sensor failures. The sufficient conditions are derived for the faulty closed - loop systems meeting such performance requirements by using matrix inequalities. The existing result on the upper bound of guaranteed cost function is improved. Based on linear matrix inequalities (LMI) approach, the reliable state - feedback controller is designed to guarantee, for possible sensor failures, the closed - loop system satisfying the pre-specified regional pole index and having the optimal quadratic cost performance. Finally, the simulative example demonstrates the validity of the proposed method.