Abstract: In order to explore the effects of waterlogging stress on the morphological structure and physiological characteristics of Bougainvillea, the pot waterlogging method was used, and the two-year-old potted seedlings of Bou-gainvillea spectabilis ‘Crimsonlake’ with similar specifications and good growth conditions were selected as the experimental materials. Then, the four treatments were set up: control (CK) , root flooding (P1) , partial flooding (P2) and complete flooding (P3). And the growth status and physiological and biochemical indexes of Bougainvillea were recorded and determined. The results showed that with the increase of waterlogging stress time, the bracts of Bougainvillea shrank, and the leaves showed the symptoms such as yellow spots and drooping. During the stress period, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) exhibited an initial increase followed by a decline. The content of malondialdehyde (MDA) content reached the peak at day 10 and then showed a decreasing trend. Compared to the control group, the proline (Pro) content in the treatments P1 and P2 showed an upward trend, while the Pro content in P3 decreased significantly. The soluble protein (SP) content showed a consistently-decreasing trend under the stress. The photosynthetic parameters of net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs）all showed a decreasing trend, with the most significant reduction in P3. However, the intercellular CO2 concentration (Ci) showed a trend of decreasing first and then increasing. The comprehensive analysis revealed that Bougainvillea could resist the lighter degree of waterlogging stress. In the early stage of waterlogging, Bougainvillea resisted the waterlogging stress by increasing the enzyme activity and osmotic adjustment substances. However, the long-term waterlogging and severe waterlogging would limit its growth. The deeper the waterlogging degree was, the longer the stress days were, and the more obvious the inhibition was.