To understand the impact of climate change on the rhizosphere microecosystems of mangrove plants, this study conducted controlled experiments on the mangrove plant Avicennia marina, in which combined stress was simulated with day/night temperature (control: 28/25°C; extreme low temperature: 8/5°C; extreme high temperature: 40/37°C) and inundation duration (control: 10 h/d; short inundation: 5 h/d; long inundation: 15 h/d). The aim was to explore the response of rhizosphere bacterial diversity, composition, and structure to combined temperature-inundation stress. The results showed that temperature and inundation stress reduced the diversity of rhizosphere bacteria, and extreme high temperature reduced the Chao1 index from 2367.6 to 2017.5 and the Shannon index from 2.40 to 2.11. Principal coordinates analysis revealed that temperature played a primary role in influencing the composition of the rhizosphere bacterial communities in A. marina. Under short inundation, the relative abundance of Gammaproteobacteria was 19%, lower than that of the control group (37%). Temperature and inundation stress significantly reduced the relative abundance of Pseudomonas, while extreme high temperature combined with short or long inundation increased the relative abundance of Geitlerinema. Additionally, compared with inundation, temperature had a greater impact on the rhizosphere community structure of A. marina, and an antagonistic effect existed between temperature and inundation, shifting the rhizosphere bacterial communities from cooperative to competitive interactions.