Abstract: The three-phase three-level neutral-point-clamped shunt active power filter (NPC-SAPF) is considered as an effective way to compensate harmonics generated by nonlinear loads in power system. In this paper, a Lyapunov-Function-based control using the decoupled NPC-SAPF state-space mathematical model is presented. An affine nonlinear model of NPC-SAPF is established in the synchronous d-q frame. Applying state feedback linearization method to the affine nonlinear model, a linearized and decoupled NPC-SAPF mathematical model is obtained. The globally asymptotically stable NPC-SAPF control system is built by choosing an appropriate Lyapunov candidate function and making sure that the function satisfies the required properties of Lyapunov stability theory. Compared with the classic proportional integral (PI) control method, the proposed control strategy has larger bandwidth and better compensation performance. The simulation and experiment results proved the validity of the proposed control strategy.