question: SIMPLE SUMMARY: Calf diarrhea is a major cause of mortality in calves, and results in high treatment costs and economic loss for the dairy and cattle industries. In addition, diarrhea usually occurs around 2 weeks after calf birth. In this study, we determined how compound probiotics influenced the gut microbiota and its effect on diarrhea rates of newborn Holstein calves. The probiotics included compound yeast (Saccharomyces cerevisiae and Kluyveromyces marxianus) and lactic acid bacteria (Lactococcus lactis subsp. lactis, Pediococcus pentosaceus, and Lactobacillus plantarum). Among them, the LS, L, and S groups are different compound probiotic groups, and the D group is the control group. Our results revealed that although probiotics did not affect the community diversity of gut bacteria in newborn calves, compound probiotics significantly increased the community richness of gut bacteria. Principal coordinates analysis using weighted UniFrac distances showed that the microbial communities of calves fed compound probiotics were relatively closely clustered, but were separate from the communities of calves in the control group. The calves fed compound probiotics also had lower rates of diarrhea. Our findings improve our understanding of the role of probiotics in regulating the gut microbiota of calves, and are of special significance to researchers in the dairy and cattle industries. ABSTRACT: We evaluated the effects of probiotic compounds on the composition of the gut microbiota. Forty newborn calves were random allocated to the lactic acid bacteria + yeast group (LS group), lactic acid bacteria group (L group), yeast group (S group), and control group (D group). Probiotics containing Lactococcus lactis subsp. lactis, Pediococcus pentosaceus, Lactobacillus plantarum, Saccharomyces cerevisiae, and Kluyveromyces marxianus were fed to calves in the three treatment groups for 15 days. The feeding process lasted 15 days. Fecal samples were collected from all calves at the end of the trial and analyzed using high-throughput 16S rRNA sequencing. Totals of 1,029,260 high-quality reads and 420,010,128 bp of sequences were obtained. Among the four groups, the alpha diversity of gut microbes was significantly higher in newborn cattle in the LS group than in those in the L, S, and D groups. Overall, the dominant phyla were Firmicutes, Actinobacteria, and Bacteroidetes, whereas Bifidobacterium was the most abundant phylum in the gut of cattle in the LS group. Newborn calves from the compound probiotic groups had closely clustered gut bacterial communities and had lower rates of diarrhea. Overall, compound probiotics regulated the intestinal microbiota community structure of newborn calves and improved intestinal health. New information relevant to the prevention of diarrhea is provided by our research in newborn calves.