In most voltage stability indices, generators are normally modeled as either PV buses or ideal voltage sources. These assumptions cannot cover the entire process of systems losing voltage stability, especially when PV generators have converted to PQ nodes in case of reactive power shortage. In this paper, an alternative generator equivalent model (GEM) is proposed for voltage stability analysis. Based on their dynamic models and real-time measurements, generators are modeled by time-varying internal voltages and impedances to capture the dynamic behaviors of generators. Furthermore, the traditional L-index is extended to incorporate GEMs for system voltage stability analysis. Simulation studies have been carried out to verify the effectiveness of the proposed new index and to show the impacts of GEM on voltage stability analysis. The simulation results of four test systems show that, in certain scenarios, incorporating GEM is necessary and can significantly improve the accuracy of voltage stability analysis