The economic performance of a fluid catalytic cracking unit (FCCU) plays an essential role in the refinery's benefit. A model-based real-time optimization (RTO) is widely applied to improve the unit's economic performance. However, reactions in an FCCU are complex. Also, it is difficult to obtain a model that is the same as the plant's, which leads to an economy loss. What is more, aperiodic perturbations in the feedstock quality make it more difficult to apply the RTO. To further improve the economic performance, an enhancing transient event trigger RTO for FCCU operation was proposed, which integrated the modifier adaptation method and trigger strategy. The modifier adaptation method was adopted to cope with model mismatch. In addition, because of the fast dynamics of a riser, the measures of a riser can partly reflect the steady feature of the whole plant. Hence, the measurements are utilized to calculate the modifiers of the objective function at a high frequency. To avoid useless calculations, a trigger event strategy is also proposed, judging whether the modified optimization problem should be resolved or not. In the simulation results, the proposed scheme was applied to an FCCU model, which was based on a refinery factory in Jiujiang, China. Different situations were demonstrated, and the results verified the efficiency of the proposed scheme.