To elucidate rhizosphere bacterial diversity from plants with different water level gradients, we examined bacterial diversity in Beijing Olympic Park plant oxidation pond, an artificial wetland. The rhizosphere bacterial diversities for Carex phacota spr., Phragmites communis, Typha orientalis, and Nymphaea tetragona grown in plants with different water levels were compared based on terminal restriction fragment length polymorphism (T-RFLP) analysis combined with analysis of variance (ANOVA). Our results showed that rhizosphere bacterial diversity decreased with increasing water levels. Different restriction enzymes, i.e.,HhaI, MspI, and RsaI, yielded the same digestion results. By combing results from digestion with these three restriction enzymes, RF combination numbers from PAT alignment also decreased with increasing water levels, consistent with the results of single restriction enzyme digestion. Further analysis showed that RF numbers in cultured rhizosphere bacteria changed significantly with the increase in water level; in contrast, the RF numbers of uncultured bacteria did not change significantly. Under different water gradients, β-Proteobacteria exhibited the most significant variations among the four plants, possibly because the increase in water level may have reduced the abilities of the different plants to secrete oxygen, thereby affecting the survival of plant rhizosphere aerobic bacteria. The triangular had the highest number of rhizosphere bacterial genera, followed by reeds, cattails, and finally water lilies. The abundances of the aerobic bacteria Alcaligenes sp., Burkholderia sp., Achromobacter sp., Delftia sp., Janthinobacterium sp., Herbaspirllum sp., Ralstonia sp., and Pelomonas sp. were probably related to the capacity of plant roots to secrete oxygen. Moreover, the oxygen-secreting capacity of rhizospheres and root exudates varied because wetland plants with different water level gradients exhibited different growth conditions and metabolic activities, affecting rhizosphere bacteria growth and reproduction. The most dominant organisms in the rhizosphere bacterial communities of these four plants were Proteobacteria, which function in the removal of nitrogen and phosphorus. The common dominant genera among these rhizosphere bacteria were Alcaligenes and Flavobacterium, which play important roles in carbon and nitrogen cycles and contribute to wetland water purification.