Enhancing crop drought tolerance is beneficial for increasing crop yield and ensuring food security. This study demonstrates that foliar application of biomass-derived carbon dots (Soy-CDs, 10 mg·L−1) can enhance the drought tolerance of maize, leading to an increase in fresh weight of maize shoots and roots (50.5 % and 54.9 %) and dry weight of maize shoots and roots (40.0 % and 37.7 %), respectively. Meanwhile, Soy-CDs altered the abundance of phyllosphere microorganisms (e.g. Proteobacteria, Deinococcus-Thermus, Verrucomicrobia, and Actinobacteria) of maize under drought stress, which enhanced the nitrogen fixation and stress resistance in maize leaves. Besides, Soy-CDs also promote Ca2+ influx and Na+ efflux in maize mesophyll cells under drought stress, facilitating the regulation of ion osmotic balance and contributing to the improvement of maize drought tolerance. Furthermore, Soy-CDs enhanced photosynthesis (55.3 %) of maize under drought stress, and the full life cycle study showed that Soy-CDs can promote the metabolism of maize kernels, ultimately improve the yield (40.5 %) and nutritional quality of maize. Therefore, this work discovers the enormous potential of biomass-derived carbon dots in improving drought resistance and quality of crop, which contributes to ensure food security.