Abstract: The optimal control for large-scale descriptor systems with symmetric circulant structure were studied. Considering that many control problems are related to the solving of the algebraic Riccati equation and Lyapunov matrix equation, a method of solving the equations is suggested for large-scale systems with symmetric circulant structure. Exploiting the special structure of symmetric circulant systems, the problem of solving these systems can be simplified to the one of solving lower dimension systems. The quadratic optimal control problem was investigated for large-scale descriptor systems with symmetric circulant structure by using the simplified solution of Riccati equation.