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Invasive species and their hybrids with native species threaten biodiversity. However, there are few reports on the drought stress adaptability of invasive species <i>Sphagneticola trilobata</i> (L.) Pruski and its hybrid with native species <i>S. calendulacea</i>. In this study, relative water content (RWC), abscisic acid (ABA), reactive oxygen species, antioxidant capacity, and photosynthetic capacity were measured in the hybrid and its parents under drought stress (13% PEG-6000). Under drought stress, the ABA content and RWC in <i>S. trilobata</i> were the highest. RWC decreased by 28% in <i>S. trilobata</i>, 41% in <i>S. calendulacea</i>, and 33% in the hybrid. Activities of the antioxidant enzymes in <i>S. trilobata</i> were the highest, and the accumulation of malondialdehyde (MDA) was the lowest (4.3 μg g⁻¹), while it was the highest in <i>S. calendulacea</i> (6.9 μg g⁻¹). The maximum photochemical efficiency (F_v/F_m) of <i>S. calendulacea</i> was the lowest (0.71), and it was the highest in <i>S. trilobata</i> (7.5) at 8 h under drought stress. The results suggest that the drought resistance of the hybrid was weaker than that of <i>S. trilobata</i> but stronger than that of <i>S. calendulacea</i>. Therefore, the survival of <i>S. calendulacea</i> may be threatened by both the invasive species <i>S. trilobata</i> and the hybrid.