In the traditional finite-set model predictive control (FS-MPC) for power converters, the cost function, considering multiple objectives of reducing the control error and limiting control actions' variation, is utilized to determine the optimal control actions. Generally, a weighting factor is adopted to achieve the trade-off between these multiple objectives in the cost function. However, this type design of cost function causes the coupling of the multiple objectives, so that none of them can be fully optimized. This coupling problem further leads to the unnecessary online computation for prediction and optimization, as well as the unnecessary control actions. This paper introduces the event-triggered (ET) mechanism into FS-MPC for power converters, so that the online computation is only activated when the triggering condition is satisfied, which means only the necessary control actions are implemented. Hence, the term of the penalty of control actions' variation can be totally removed from the cost function, so that the coupling problem can be solved. The simulation study based on a three-phase inverter have been conducted to show the effectiveness of the combination of ET mechanism and FS-MPC.