Saccharomyces boulardii(S. boulardii)， a subspecies of S. cerevisiae， has a positive impact on intestinal homeostasis in humans and animals as a probiotic that can treat gastrointestinal diseases. S. boulardii has its own phenotypic characteristics and physiological properties. However， it is genetically close to the model yeast S. cerevisiae， and it has been discussed for a long time as an independent species or divided into S. cerevisiae variants. Therefore， this paper first reviews the main genetic differences between S. boulardii and S. cerevisiae. Secondly， its ability to adapt to host physiological conditions is summarized， clarify its unique biological activities， including the optimal growth temperature and the ability to survive in the acidic environment of the gastrointestinal tract， which are the basis of its success as a probiotic. In addition， elucidating their intestinal probiotic effects in terms of various biological functions such as antitoxin properties， competitive rejection of pathogens， regulation of intestinal microbiome， stimulation of the intestinal mucosal immune system and trophic effects. Finally， the application status and prospects of S. boulardii in feed and food were summarized. S. boulardii has great potential as a novel probiotic preparation for human health and companion animal industries.