Cynanchum forrestii Schltr, an erect perennial herb of Asclepiadaceae, is a wild plant with extremely small population(WPESP) in China. This unique plant grows in a variety of habitats such as plateau and mountain at altitudes of 1000-3500 m. The root of C. forrestii is often used as a substitute for the traditional Chinese medicine "Baiwei". In Jiulong County, Ganzi Tibetan Autonomous Prefecture, western Sichuan Province, China, this plant is confined to alpine meadows in valleys at the altitude of 3100-3500 m. The rhizosphere is a part of the soil ecosystem where plant roots, soil and the soil microorganisms interact with each other. Soil microorganisms actively participate in soil material transformation and play a leading role in nutrient cycling by influencing the transformation of mineral elements. Most of the nutrients needed of plants come from soil and enter plants through rhizosphere interaction. The chemical element characteristics of plants can reflect the supply of nutrients to the soil. The study of plant and soil stoichiometric characteristics helps to understand the growth strategies of plants and their adaptability to the environment. Investigating the stoichiometric characteristics and element enrichment of the C. forrestii-rhizosphere soil system under the alpine environment will help to analyze the survival strategies of the extremely small populations and their adaptability to the environment. In this study, we investigated the effects of rhizosphere soil nutrients and bacterial community on population characteristics and photosynthetic characteristics of C. forrestii in the alpine meadow of Jiulong County by using plot and line transect sampling methods, physiological and biochemical analysis and Illumina-MiSeq high-throughput sequencing technology. The results showed that compared with the non-rhizosphere soil, the rhizosphere soil had higher P, C/P and N/P and lower C/N, and increased soil organic matter (SOM), total phosphorus (TP), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AK). The Pearson correlation analysis showed that the value of N, C/P, N/P in C. forrestii stem were significantly positively correlated with the rhizosphere soil P, while the value of P and C/N were significantly negatively correlated with the rhizosphere P. High-throughput sequencing showed that the dominant bacteria in rhizosphere soil/non-rhizosphere soil included 6 groups. Compared with non-rhizosphere soil, the relative abundance of Proteobacteria and Gemmatimonadetes in rhizosphere soil was higher, while the relative abundance of Acidobacteria, Bacteroidetes, Actinobacteria and Firmicutes was lower. The relative abundance of Bacteroidetes decreased by 45.53%, and the relative abundance of Proteobacteria increased by 32.89%. Redundancy analysis (RDA) results showed that the relative abundance of Proteobacteria was positively correlated with soil C, N and P contents. The average plant height of C. forrestii was 27 cm, which was higher than the average height of other plants in the community. The proportion of above ground biomass reached 41.24%, and the population density and niche width also were larger than those of other plants. With the increase of plant height and leaf area, the photosynthetic pigment contents and Chla/Chlb raised first and then decreased, but leaf mass per area (LMA) had little change. Plants had enrichment effect on soil elements, the relatively high enrichment capacity for Ca, Mn, Na, K and P, and high transfer capacity for P, Ca, and K. Analysis of C, N, P stoichiometry showed that the C/N, C/P and N/P in C. forrestii leaves were higher than those of roots and stems, and the N/P of each organ was less than 14, indicating that N was the limit factor. In general, C. forrestii enriched beneficial soil microorganisms to improve the nutrient status of the rhizosphere soil, enhanced the absorption and transfer of elements such as Ca, Mn, Na, K, and P in plants, and promoted the ability to resist freezing and radiation. With the advantages of plant height and leaf area, it made up for the defect of low photosynthetic pigment content, thereby improving the interspecific competition ability and fitness of C. forrestii in the alpine environment, but intraspecific competition was intensified, which resulted in uniform distribution of plant clusters. It was speculated that the intense intraspecific competition was one of the reasons for the limited distribution of C. forrestii.