Invasive plants potentially threaten urban ecosystems, which deserve more attention. This paper took invasive plants Bidens pilosa and Sphagneticola trilobata as a case study, to explore urban invasive plants' influence on species and functional diversity of herbaceous plants. Different levels of independent and joint invasion effects on herbaceous community's species diversity and functional diversity were analyzed. The results showed that:(1) Margalef species richness index, Shannon-Wiener diversity index, Simpson dominance index, and Pielou evenness index exhibited significantly negative correlation with the invasive plants' coverage (P<0.05, 0.5865<R²<0.9356). (2) Functional richness index (FRic), Functional evenness index (FEve), and Rao's quadratic entropy index (FD_Q) had specific correlation with the invasive plants' coverage (0.0000<R²<0.2211). (3) Community-Weighted Mean plant height (CWM_H) had specific positive correlation with invasive plants' coverage (0.0716<R²<0.2262). (4) Compared with the non-invasive samples, the light invasion of Bidens pilosa significantly increased the species diversity (P<0.05), but the severe independent invasion of Bidens pilosa and Sphagneticola trilobata significantly reduced species diversity (P<0.05), and all levels' independent and joint invasions of Bidens pilosa and Sphagneticola trilobata also significantly increased CWM_H (P<0.05). (5) As found by analyzing different green space types separately, the independent and the joint invasion of Bidens pilosa both significantly increased the species diversity of all green space types (P<0.05), while Sphagneticola trilobata had no significant effect on the community species diversity. (6) The ecological effect between Bidens pilosa and Sphagneticola trilobata maybe was antagonistic. The results provide a reference for further studies on plant invasion' effects on urban herbaceous plant communities and supply a basis for effective control of urban alien plant invasions.