Studies on the effects of invasive plants on native herbivores often only concern about short-term effects, and few studies have focused on the long-term effects of invasive plants on herbivores. We investigated the development of Spodoptera litura to the second generation on the invasive plant Phytolacca americana and the exotic non-invasive plant Phytolacca icosandra, meanwhile, we tested the impacts of the P. americana on the S. litura through laboratory bioassay, oviposition preference and detoxifying enzyme activity analysis. The results show that S. litura have feeding and oviposition preference to P. icosandra, the larval weight and oviposition preference index (OPI) of S. litura feeding on P. icosandra are higher. However, the developmental duration of S. litura on P. icosandra is shorter than that of P. americana; the activities of Acetyl cholinesterase (AchE) and Glutathione-S-transferase (GST) of S. litura feeding on the leaves of the P. americana were higher than those of feeding on artificial diet and P. icosandra. There is no significant difference of activities of AchE and GST between S. litura feeding on artificial diet and P. icosandra. These findings have important implications for the evaluation of the impacts of invasive plant P. americana on native herbivores in the local ecosystem and explain that invasive plant has higher resistance to herbivores and suffer less damage than exotic non-invasive plant in the invaded range.