Animal growth traits are important and complex traits that determine the productivity of animal husbandry. There are many factors that affect growth traits, among which diet digestion is the key factor. In the process of animal digestion and absorption, the role of gastrointestinal microbes is essential. In this study, we transplanted two groups of sheep intestinal microorganisms with different body weights into the intestines of mice of the same age to observe the effect of fecal bacteria transplantation on the growth characteristics of the mouse model. The results showed that receiving fecal microbiota transplantation (FMT) had an effect on the growth traits of recipient mice (P < 0.05). Interestingly, only mice receiving high-weight donor microorganisms showed differences. Use 16S rDNA sequencing technology to analyze the stool microorganisms of sheep and mice. The microbial analysis of mouse feces showed that receiving FMT could improve the diversity and richness of microorganisms (P < 0.05), and the microbial composition of mouse feces receiving low-weight donor microorganisms was similar to that of the control group, which was consistent with the change trend of growth traits. The feces of high-weight sheep may have higher colonization ability. The same five biomarkers were identified in the donor and recipient, all belonging to Firmicutes, and were positively correlated with the body weight of mice at each stage. These results suggest that FMT affects the growth traits of receptors by remodeling their gut microflora.