Diaphorina citri Kuwayama, a major pest during the citrus shoot stage, is the primary vector of the bacterial that causes Citrus huanglongbing in the field, posing a serious threat to the healthy development of the citrus industry. Elucidation of the population genetic structure of this insect is therefore indispensable for the devising of targeted and effective management strategies. In this study, the mitochondrial cytochrome c oxidase subunit I (COI) gene was employed as a molecular marker to analyse the population genetic structure and diversity of D. citri across Jiangxi Province, China. Eight haplotypes (designated as Hap_1 ~ Hap_8) were identified in all the COI gene sequences of 316 D. citri individual samples from 16 distinct populations. Hap_1 was the dominant haplotype in all populations, accounting for 92.7% of the total samples. The observed pattern of the haplotype network manifested as a typical star-shaped structure, with Hap_1 occupying the central position, thereby suggesting its ancestral maternal status for the surveyed populations. The overall haplotype diversity index (Hd) was 0.139 and nucleotide diversity index (Pi) was 0.00022, suggesting a low level of genetic diversity within the entire population. The differentiation index (Fst) of XYYS population between others was found to be greater than 0.15, indicating a high level of differentiation level, while a low level of differentiation among the other populations was found. The neutrality test and mismatch distribution analyses indicate that D. citri populations in Jiangxi Province have undergone a recent rapid dynamic expansion. The results of the study provide fundamental data for a systematic understanding of the population genetic structure of D. citri in Jiangxi Province.