Benzene, toluene, ethylbenzene and xylene, collectively known as BTEX, are the aromatic organic pollutants with the most detected rates in chemically polluted areas. To investigate the effects of long-term BTEX contamination on soil and groundwater microbial community structure and metabolic potential, superficial soil, groundwaterand deep soil samples were collected from a relocated chemical plant in Jiangsu Province, and analyzed by using 16S rRNA gene amplicon sequencing and metagenomics sequencing techniques. The results showed that long-term BTEX contamination significantly altered the microbial community structure and diversity compared to uncontaminated soil, with the most significant alterations in Proteobacteria. Co-occurrence network analysis showed that microbial network complexity and community stability decreased with increasing sample depth in contaminated sites. BTEX metabolic function gene annotations indicated a higher abundance and diversity of contaminant metabolism genes in groundwater samples, and the complete aerobic degradation pathway was present in both groundwater and superficial soil, but the abundance of anaerobic degradation genes was more abundant in groundwater. The benABC and bcrCBAD gene clusters in the BTEX degradation pathway were more complete in superficial soil, but the construction of a phylogenetic tree of bamA, a key gene in BTEX opening, suggested that new BTEX ring-opening genes may be present in groundwater. These results demonstrate the existence of highly diverse microbial communities and degradation pathways in different habitats contaminated by BTEX over long term and provide a scientific basis for the microbial remediation of relevant contaminated sites.