Application of phosphate-solubilizing bioinoculants is regarded as a sustainable approach for improving peanut (Arachis hypogaea) productivity in Ultisols. In this study, an acid-tolerant phosphate-solubilizing bacterium, Pantoea sp. IP1, was used to evaluate its effects on peanut yield regulation. A pot experiment was conducted to determine rhizosphere colonization, plant biomass, yield components, and soil chemical properties. High-throughput sequencing, microbial co-occurrence network analysis, and partial least squares path modeling (PLS-PM) were applied to elucidate the relationships among rhizosphere microbial communities, soil properties, and peanut yield. The results showed that strain IP1 maintained high viable cell numbers in the peanut rhizosphere throughout the 35 days colonization period. Compared with control, pod number and dry weight of peanut were significantly increasing by 44.5% and 56.16% at maturity, respectively. Absorption and translocation of phosphorus were enhanced, and contents of available phosphorus and soil organic matter were significantly increased by 40.4% and 21.3%, respectively. Moreover, the relative abundances of key rhizosphere microbial modules, which were involved in nutrient transformation, were markedly increased at the pod-setting and maturity stages, particularly Gemmatimonas and Aspergillus. The relative abundances of potential phytopathogens decreased, such as Fusarium. Partial least squares path modeling indicated a strong direct statistical association between IP1 treatment and peanut yield improvement, while soil AP, SOM, and key microbial taxa may be involved in indirect regulatory processes. Overall, IP1 represents a highly efficient phosphate-solubilizing plant-growth promoting bacterium with considerable application potential, and these findings provide a theoretical basis for the further development and field application of phosphate-solubilizing bioinoculants in acidic Ultisols regions.