Extreme drought and insect herbivores can affect plant community non-independently, and their interaction may be influenced by drought pattern. However, few studies have explored the interaction on plant community structure, and no study has investigated whether the interaction is affected by drought pattern. We explored the interaction of different extreme drought patterns and insect herbivores with a manipulated experiment in a semiarid grassland. There were three treatments for drought: control—ambient precipitation; chronic drought—66% precipitation reduction in the growing season (May-August); intense drought—completely exclusion of rain events from June to July. Herbivores removal and present treatments were imposed within each drought treatment. We found that although herbivores had no significant effects on the impacts of droughts on total species richness, it alleviated the impacts of chronic drought on total cover, and the alleviating role decreased under intense drought. Comparing with intense drought, more increasing of grass cover led to more alleviation under chronic drought associated with the decrease of forb which has low leaf carbon and dry matter content, along with high starch, calcium, magnesium and manganese concentration. These results indicate that the interaction of drought and herbivores is affected by drought pattern, and the changes in leaf traits that reduce herbivores feeding in grass might alleviate the impact of drought on grassland.