An optimal robust pole assignment scheme is presented in this paper. Robustness is measured by the spectral condition number of the closed loop eigenstructure. Since the spectral condition number is nondifferentiable, an approximate differentiable objective function, which includes an index p , is introduced. As p tends to infinity, the optimizer for the approximate objective function converges to that for condition number. For each p , a steepest descent method is used to find the optimizer. In our example, the optimizer converges within a very small p .