Abstract: The high biodiversity and economic costs associated with invasive plants have promoted research to identify traits associated with invasiveness. At present, most research has been based on comparisons between invasive and native species but, in this paper, two invasive species with different levels of invasiveness, Eupatorium adenophorum and Gynura sp., were studied. Both species were grown under four different relative irradiances (RI 12.5%, 36%, 50%, 100%) for 50 days, and we then measured their biomass allocation, leaf morphology and growth properties to compare their light acclimation abilities and growth strategies.The two species exhibited typical leaf morphological responses to different light conditions. At low light levels, plants enhanced light interception by means of increased biomass allocation to leaves and formation of large, thin leaves with high specific leaf area (SLA), leading to a high leaf area ratio (LAR). At high light levels, plants reduced transpiration losses and increased carbon gain by making small-sized, thick leaves with a low SLA, leading to a low LAR and leaf area to root mass ratio. Under most light regimes, E. adenophorum was higher in leaf mass ratio (LMR), leaf mass fraction (LMF), LAR, root mass ratio (RMR) and root mass to crown mass ratio (R/C), but lower in supporting organ biomass ratio (SBR), MLA and branch number as compared to Gynura sp. Leaf mass ratio, LMF, and leaf area index of E. adenophorum were the highest under 100% irradiance than under other light regimes and higher than for Gynura sp.; however, for SBR, these patterns were reversed. Under 100% irradiance, leaves were much more self-shaded in E. adenophorum than in Gynura sp. This might be an adaptive strategy that supports the vigorous invasiveness of this species because a high-shaded canopy could prevent other plant species from surviving and competing. The number of branches of Gynura sp. was greater under 100% irradiance than under other light regimes and significantly more than for E. adenophorum. This might be an adaptive strategy for Gynura sp. because a greater number of branches can produce more flowers and thus more seeds. For both species, an increase in light intensity resulted in an increase in net assimilation rates (NAR) and growth response coefficient of NAR (GRCNAR), whereas mean leaf area ratio (LARm) and growth response coefficient of LARm (GRCLARm) decreased. GRCLARm was higher than GRCNAR at all times. The relative growth rate (RGR) of E. adenophorum increased with an increase in light intensity but decreased in Gynura sp. With a decrease in light intensity, both E. adenophorum and Gynura sp. grew taller and produced more branches to intercept more light energy. The biomass allocation strategy differed between the two species: RMR decreased and SBR increased in E. adenophorum, while RMR increased, and SBR decreased in Gynura sp. All of the results presented above indicate that E. adenophorum was able to acclimate better to different light conditions, especially to low light regimes, than Gynura sp., and its better ability to acclimate might explain its greater invasiveness.