This study aims to determine the functional traits and reproductive allocation (RA) strategy of the invasive plant Conyza canadensis across different invasion degrees along a latitude gradient in China. Invasion degree did not affect the functional traits and RA strategy of C. canadensis significantly. The high proportion of reproductive biomass (allocating approximately 20% of total biomass into reproductive behaviors) of C. canadensis across different invasion degrees can achieve a fitness advantage in broadening its habitat niches and can eventually attain a successful invasion. The higher proportion of reproductive biomass of C. canadensis in warm temperate and subtropical monsoon climatic zones may play an important role in its successful invasion in the two climatic zones in China. One possible reason for this is that eastern China and northern China, in which C. canadensis vigorously occurs, have the same or similar climate as their natural habitat in the original distribution region. The proportion of reproductive biomass of C. canadensis positively correlated with its total biomass, aboveground biomass, belowground biomass, and vegetative biomass, as well as with its height and leaf size. Meanwhile, temperature rather than annual sunshine hours or annual precipitation was determined to be the most important environmental factor that triggers pronounced effects on the RA strategy of C. canadensis.