<p>This paper investigates the issue of event-triggered asymptotic tracking control for a class of uncertain nonlinear systems with time-varying parameters (TVPs) and full-state constraints. The uncertain parameters and unknown disturbances in the considered system are time-varying, which makes the design of the controller more challenging. By using time-varying barrier Lyapunov functions and command filter-based backstepping method, an event-based adaptive controller is presented to achieve zero error tracking under state-constrained conditions. Then, the effects of TVPs and external disturbances are compensated for by means of a bounded estimation method and some integrable time-varying functions. The stability analysis proves that the designed controller ensures that all the closed-loop signals of the system are bounded and the system states do not violate the constraints, while significantly reducing the number of samples. In the end, the effectiveness of the proposed control method is demonstrated by two simulation examples.</p>