This study investigated the effects of different folic acid and vitamin B₁₂ supplemental levels in diets on the caecal microflora structure of gosling. A total of 360 one-day-old Wulong geese were randomly divided into 6 groups, each group had 6 replicates and each replicate consisted of 5-male and 5-female geese. A 2×3 two-factor (folic acid×vitamin B₁₂) crossed equal replication factorial design was used in this experiment, the folic acid supplemental levels in diets were 0.55 and 2.50 mg/kg, respectively, and the vitamin B₁₂ supplemental levels in diets were 0.009, 0.018 and 0.036 mg/kg, respectively. The folic acid and vitamin B₁₂ supplemental levels in diets of groups Ⅰ to Ⅵ were 0.55 and 0.009 mg/kg, 2.50 and 0.018 mg/kg, 0.55 and 0.036 mg/kg, 2.50 and 0.009 mg/kg, 0.55 and 0.018 mg/kg, 2.50 and 0.036 mg/kg, respectively.The experiment lasted for 4 weeks. The 16S rRNA high throughput sequencing technology was used to investigate the microbial diversity in the caecum of gosling after the feeding experiment. Based on the Illumina HiSeq sequencing platform, a small fragment library was constructed by paired-end sequencing, and then carried on α diversity and significantly different species analysis. The results showed as follows:1) dietary supplemented different levels of folic acid and vitamin B₁₂ had significant effects on final body weight (FBW) and average body weight (ADG) of gosling (P<0.05), but had no significant effect on feed/gain (F/G) (P>0.05). The FBW and ADG in group Ⅳ were significantly higher than those in the other 5 groups (P<0.05). 2) The operational taxonomic unit (OUT) number, ACE index and Chao1 index of group Ⅳ were the highest, which demonstrated that the species abundance of group Ⅳ was higher than that of the other 5 groups. Clustering analysis showed that the caecal microflora of groups Ⅰ and Ⅵ had the highest similarity, and that of groups Ⅰ and Ⅱ had the lowest similarity. 3) Firmicutes, Bacteroidestes and Proteobacteria were the predominant bacteria phylums. Caecal abundance microflora in phylum level was changed by dietary supplemented different levels of folic acid and vitamin B₁₂, and the Firmicutes, Bacteroidestes and Proteobacteria changed obviously. A total of 91 different genera were detected in the ceacal samples. From groups Ⅰ to Ⅵ, 86, 84, 83, 87, 87 and 83 genera were detected, respectively. The higher relative abundant genera were Desulfovibrio, Bacterium, Bacteroides, Alistipes and Barnesiella. The abundance of dominant genera existed major difference among different groups. In species level, Bacilus had an absolute advantage in the caecal microflora of each group, the relative abundance of Bacillus in groups Ⅰ to Ⅵ was 93.5%, 93.7%, 87.8%, 95.2%, 93.4% and 87.9%, respectively, and no significant difference was found among groups (P>0.05). It is concluded that adding 2.5 mg/kg folic acid and 0.009 mg/kg vitamin B₁₂ into the diet can optimize the caecal microflora structure, and increase the abundance of beneficial microorganisms, thus to improve the performance of gosling.