Abstract: Design of robust H_∞ decentralized state feedback controller is considered for large-scale interconnected systems with uncertainty value bound in state,control and interconnected matrices.A sufficient condition for existing decentralized robust H_∞ state feedback controller is derived based on the boundedness real lemma.This condition is expressed as the solvability problem of nonlinear matrix inequality(NLMI).A controller which can make the large-scale closed loop system robust and stable and satisfy the given H_∞ performance is obtained by homotopy iterative method.Simulation results demonstrate the validity of the method.