This paper develops a new design method of parallel- distributed-compensation (PDC) fuzzy- sliding- mode controller. This controller is then applied to control an ecological system. A new fuzzy-blending- sliding-surface based on the PDC concept is introduced. By using this sliding-surface, a PDC-based sliding-mode controller is designed for an ecological system which is a multi-input multi- output nonlinear system subject to unpredictable but bounded disturbances. The Lyapunov stability condition is achieved in this design, so that the system’s stability can be guaranteed. This PDC-based fuzzy-sliding-mode controller is applied to keep biomasses of the ecological system within a small neighborhood of the unique nontrivial optimal equilibrium state. By applying this controller, the accumulative yield of harvest is better than that by using state feedback control and open loop control.