Abstract: he problems of spillover management of flexible spacecraft dynamic output feedback control systems are studied.Parameter optimization and orthogonal subspace methods of allevi-ating spillover of the systems are presented. One robust measure of the control svstems is defined in tenns of closed-loop poles and used to justify the final design。 Through adding constraint to optimal design index,a synthetic method of optimal control system design and spillover allevia-tion is made.Using the method the spillover is efficiently alleviated, so the interaction of control-ler and residual modes is redueed and robustness of the control system is improved

Key words: flexible spacecraft, robust control, spillover management