Abstract: The active noise control (ANC) is studied for the acoustic system. The research shows that the active noise controls adopted feedforward technology or feedback technology is correspond to adaptive control with measurable noise or immeasurable noise. An adaptive active noise variable structure control with a sector is derived for the acoustic system with uncertain parameters. An on-line learning algorithm is proposed for identifying the Uncertain path parameters. The stability of closed loop system is proved in the Lyapunov's sense. A simulate example is given to show that the adaptive active noise variable structure control is a very effective control method.