<p>This paper investigates the distributed output formation tracking for heterogeneous nonlinear multi-agent systems, where agents may have different system orders, unknown nonlinear dynamics, and time-varying control input matrices. Specifically, the dynamics of both the leader and followers are subject to uncertainties. An adaptive fuzzy formation strategy based on discrete event detection and communication is proposed. First, a periodic event-driven distributed observer is designed to estimate the state of the uncertain leader, where the sampling period <i>T</i> is carefully chosen. Events are detected only at pre-specified sampling instants, and data transmission occurs only when the triggering condition is satisfied. In this way, both communication and computational resources can be saved. Due to both the heterogeneous system orders and non-differentiable signals caused by discontinuous transmission, the standard backstepping technology cannot be directly used here. To address the technical challenges, a novel reference trajectory generator is specially designed, featuring different orders for various followers to handle heterogeneous orders. The generated trajectory can approximate the leader’s output with adjustable precision despite unknown uncertainties, and is guaranteed to be higher-order differentiable. Further, a backstepping-based adaptive fuzzy controller is developed to achieve the desired formation tracking. Finally, simulation results demonstrate the effectiveness of the proposed approach.</p>