Abstract: Based on fuzzy logic approximation principle, a new fuzzy decentralized controller is designed for a class of nonlinear interconnected systems with unknown dynamics. Two cases are discussed, i.e., whether or not the interconnected terms satisfy certain general restrict conditions. Different methods are adopted to counteract the affection of the interconnected terms to the whole system. The mode transformation function is used to realize the changing between the fuzzy indirect adaptive controller and fuzzy sliding mode controller, which keeps the state of the system changing in a close bounded set. By using Lyapunov method, it is proved that the close-loop system is stable and the tracking errors converge to a neighborhood of zero. The result of the emulation proves the validation of the designed controllers.