This paper addresses the event-triggered prescribed-time control problem for a class of high-order nonlinear systems based on finite time-varying gain. Due to the existence of unknown time-varying gain and system uncertainties, the resultant control with prescribed-time convergence performance becomes nontrivial. The problem becomes even more complex due to the use of event-based communication instead of continuous communication. To tackle the aforementioned challenges, this paper proposes an event-triggered prescribed-time stabilization approach with the following key steps. Firstly, we establish a new prescribed-time stability lemma to overcome the technical difficulty arising from the prescribed-time controller design, and stability analysis. Secondly, we given the controller design procedure upon using the backstepping technique. Thirdly, we redesign the time-varying trigger conditions based on time-varying functions and saturation ceilings, which allows the controller terminal jitter to be mitigated and the controller to be implemented straightforwardly in practice. Meanwhile, we incorporate the compensation technique upon using symbolic functions and time-varying finite decay gains into the controller design to handle the error caused by event-based communication. Furthermore, the proposed control scheme avoids Zeno behavior. The numerical simulation confirms the effectiveness of the proposed control scheme.