Plant invasion is major global driver to structure and functioning of natural communities. Species diversity is a fundamental determinant of community regeneration and dynamics through flowering phenology and groups. However, the impacts of plant invasion on native plant flowering phenology and how species diversity regulates the process remain unclear. We conducted a field experiment to assess the effects of plant invasion (Solidago canadensis) and community species diversity on flowering phenology of native plants from different flowering functional groups (FFGs) at community and species levels. We found that at community level, plant invasion shortened flowering duration (FD), and reduced flowering synchrony of native communities. Furthermore, high diversity reduced the negative impacts of plant invasion on flowering synchrony. Among FFGs, the late and mid flowering species responded more negatively to plant invasion than the early flowering species. SEM indicated that plant invasion suppressed plant height and FFD or LFD by reducing light availability to native plants, which in turn affected flowering phenology. However, high diversity counteracted the negative effects. Our findings confirm the role of high species diversity in resisting alien plant invasions on flowering phenology and reproduction of native plant communities, and suggest that high diversity with different FFGs should be considered to efficiently restore native communities invaded by alien plants such as S. canadensis.