In this study, the rhizosphere soils of Achyranthes bidentata, which was grown in a monoculture for multiple years, were investigated for analyzing the major elements, trace elements and rhizosphere microbial community structure by means of agricultural chemistry and phospholipid fatty acid (PLFA) analysis techniques. The results showed that consecutive monocultures of A. bidentata increased the contents of major elements (total phosphorus, alkaline hydrolysis nitrogen, available phosphorus, and available potassium). However, the ability of consecutive monocultures to change the total nitrogen content and total potassium was not obvious. In addition, total calcium, total magnesium, total manganese, and available zinc contents also increased with the increasing years of monoculture. Further analysis of PLFA profiles showed that there were no obvious differences in the rhizosphere microbial community structures between the control and newly planted A. bidentata. Besides, different results were depicted by 10 years and 30 years of consecutive monoculture, which showed that the total PLFA, bacteria (especially G^-), and fungal content increased significantly, and the G⁺/G^- ratio decreased with increasing years of monoculture. Moreover, some microbes involved in material cycling and lignin degradation, such as Hydrogenobacter, fungi (PLFA18:2ω6,9), and some beneficial bacteria including Pseudomonas increased significantly with increasing years of monoculture. These results suggest the important biological basis for the promotion mechanism of A. bidentata under a monoculture system. The case study exemplifies the ecological significance of rhizosphere microbial structure and its functional diversity in monoculture promotion or monoculture inhibition.