Abstract: Heavy metal pollution remains a major constraint affecting the safe production and sustainable utilization of cultivated land. Developing efficient and convenient remediation technologies for heavy metal contamination is crucial for ensuring national food security. As a plant growth regulator, humic acid (HA) demonstrates beneficial effects on rice growth. However, a systematic understanding of the impact and mechanisms of foliar HA application on heavy metal uptake in rice is still lacking. This study investigated the effects of varying HA spray dosages, which were 0 (control), 4.40, 8.80, 13.20 and 17.60 kg·hm⁻², on rice growth and Cd uptake through pot experiments and analyzed the response of phyllosphere bacterial communities to HA application and their relationship with Cd uptake, using high-throughput sequencing technology. All HA treatments enhanced rice growth and Cd resistance in Cd-contaminated soil. Compared with the control, HA application increased plant height, root length, fresh weight, biomass and grain yield by 6.33%–26.44%, 12.65%–48.23%, 16.86%–51.53%, 19.52%–59.93%, and 4.11%–13.58%. The growth-promoting effects on fresh weight, biomass intensified with increasing HA dosage. Furthermore, HA application significantly reduced Cd content in rice roots, stems and leaves, and grains by 2.74%–8.87%, 6.17%–16.48%, and 5.95%–18.01% respectively. HA treatments significantly altered the structure and increased the diversity of phyllosphere bacterial communities; however, high HA dosages significantly reduced the network complexity of phyllosphere bacterial communities. Plant Cd content was significantly correlated with the complexity of bacterial community interactions rather than the community structure or diversity of phyllosphere bacteria communities. These findings indicated that foliar HA application effectively improved Cd resistance in rice, modified phyllosphere microbial communities, and enhanced both yield and crop safety. Furthermore, HA exhibited a distinct nonlinear dose-response effect. Under the experimental conditions, an optimal foliar HA dosage of 13.20 kg·hm⁻² was identified as most conducive to rice production in Cd-contaminated soil.