Selenium (Se) is a naturally occurring metalloid element, which is essential to the health of human and other animals in trace amounts but is harmful in excess. As a micronutrient, Se owns multiple biological functions including regulation of vitamins absorption, participation in electron transfer, body metabolism regulation, affection towards the reproductive function of humans and animals, antitumor, free radical scavenger, antiaging, and antagonism of toxic elements, playing important roles in improvement of the human body’s immune system and the prevention of various diseases [1– ۴]. Currently, many Se-enriched foods are available in the market, in which Se additives are mainly in the form of inorganic and organic Se. Generally, Se in organic forms has better bioavailability and is less toxic compared with inorganic selenium with poor conversion and high toxicity to some extent [5–۸]. Nowadays, various available sources of organic Se, namely, Se-enriched yeast [9–۱۱], selenomethionine [12– ۱۴], Se-enriched probiotics [15], heterotrophically produced Se-enriched alga [16, 17], and Se-enriched plants [18, 19], have been investigated over time. Among these organic Se, the main organic Se source used in practice is Se-enriched yeast, in which Se is present predominantly (94 ± ۵%) in the form of protein-bound L-selenomethionine [20]. As a kind of organic Se, Se-enriched yeast owned the advantages of high effectiveness, lower toxicity, and better nutrition. However, the composition of the raw products of Se-enriched yeast (obtained by culture and whizzer) is complex and may contain unconverted inorganic selenium, possessing obstacles for the practice application in food industry. Therefore, in this work, further works were made for the more secure and easily adsorbed bio-Se. The yeast cells were lysed by sonication after a period of growth with sodium selenite and dialyzed to remove the free inorganic selenium. Finally, the bio-Se obtained from yeast was produced. Theoretically, compared with raw products of Se-enriched yeast, bio-Se is a safe and effective formulation which holds important practical value. However, the toxicology of the bioSe obtained from yeast was not fully convinced yet.