Abstract: In order to reduce the toxicity of inorganic arsenic and improve the bioavailability of selenium, this study used yeast to convert inorganic selenium into synthesize selenium nanoparticles (SeNPs). Through the screening of seven probiotic yeast strains, Saccharomyces cerevisiae ATCC 18824 was finally screened as the best nano-selenium synthesized strain and its optimal nano-selenium synthesized conditions were established. The synthesized nano-selenium was observed and characterized in terms of structure and morphology using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, the safety of nano-selenium was verified by feeding experiments in mice for 30 days. ATCC 18824 synthesized nano-selenium exhibited good dispersion, presenting Se⁰ nano selenium monoliths of uniform size and full spherical shape, and the Na₂SeO₃ addition was controlled to be optimal at 0.5~1.5 mg/mL, 30 °C, and 60~72 h incubation. It was also found that nano-selenium was synthesized intracellularly and gradually released over time, ultimately excreted within 72 hours. The 30 days feeding experiment showed that nano-selenium had no significant effect on body weight change, organ index, blood routine and biochemical analysis, and major organ tissues in mice, verifying the safety of nano-selenium. Based on the results of the study, the present study successfully developed yeast-derived nano-selenium milk tablets with good sensory evaluation and rich nutritional content of 12.67 μg/g, 16.67 μg/g, and 33.33 μg/g of selenium, its nutritional value was higher than part of the commercially available milk tablets, showing its potential as a novel and safe food additive in the food processing industry application value in the food processing industry.