Foxtail millet (Setaria italica (L.) Beauv) is an important crop for both basic research and sustainable dryland agriculture, due to its rapid growth, high seed yield, strong stress tolerance, and rich nutritional qualities. Multiple mutagenesis approaches have been used to broaden foxtail millet germplasm resources, among which heavy ion beam (HIB) irradiation has emerged as a powerful tool for inducing genetic variations in plant breeding. However, compared with other model species, genetic resources in foxtail millet remain limited, and the specific effects of HIB radiation on this crop are not yet fully understood. In this study, seeds of foxtail millet (Yugu 24) were irradiated using six different carbon-ion beams (CIB, 100 Gy-500 Gy), a commonly used HIB mutagen. Then, the mutagenic effects were evaluated in the M1 generation, conducted large-scale phenotype screening in the M2 generation, and analyzed the anatomical, physiological, and molecular mechanisms of stable leaf mutants. M1 plants exhibited dose-dependent responses, with the optimum CIB dose for Yugu 24 ranging from 110 Gy to 140 Gy. From 3100 M2 plants, we identified 56 individuals exhibiting obvious phenotypic variations, resulting in an overall mutation frequency of 1.81 % under CIB irradiation. High frequencies of leaf morphological mutations was observed in the M2 population. Stable leaf mutants were identified and further characterized in the M4 generation, which displayed distinct phenotypic variations, including changes in chloroplast structure, stomatal characteristics, and photosynthetic pigment content. Collectively, these findings establish a theoretical foundation for applying CIB irradiation in foxtail millet mutation breeding. Furthermore, the CIB-induced mutant library of Yugu 24provides a valuable resource for future functional genomics research on foxtail millet.