In this paper, the robustness of the n/2/P/Cmax scheduling problem is studied by using a property of Abelian semi-group which contains identity element on the real number set R+. According to the practical problem, we construct a class of process perturbation system model, propose the system output expression, and give its some properties. Finally, by the definition of optimal robust scheduling, we prove that: (1) if ω* is the optimal robust scheduling of the reference system, then ω* must be its optimal scheduling; (2) Yue-Han's optimal scheduling of the reference system must be its optimal robust scheduling.
