Abstract: Human activities exert a significant impact on the global atmospheric circulation pattern, resulting in the increasing amplitude, frequency and duration of extreme drought events, which have more negative impacts on grassland ecosystem. In this study, we conducted a four-year extreme drought experiment to investigate the responses of plant community traits to extreme drought as well their consequences on ecosystem functions in a meadow grassland, Inner Mongolia. The results showed that experimental extreme drought exerted no significant effect on plant community traits, which indicated that plant are insensitive to extreme drought and plant community adopted tolerance/conservative strategy under water stress conditions. The relationships between plant community trait diversity and aboveground net primary productivity were not observed under extreme drought conditions, which was inconsistent with the diversity hypothesis. On the other hand, aboveground net primary productivity was mediated by the community-weighted trait means under extreme drought conditions. Specifically, aboveground net primary productivity was positively correlated with community-weighted plant height and negatively correlated with community-weighted leaf carbon concentrations. These results highlighted the great effects of dominated species on ecosystem functions, being in line with mass ratio hypothesis. Overall, these results are of great significance for revealing the processes and mechanisms underlying the functional responses of grassland communities to extreme drought, providing a scientific basis for vegetation protection and management in grassland ecosystem.