(Purpose) To investigate the effect of vitamin deficiency on the cecal bacterial communities, (Methods & Results) two bacterial 16S rRNA gene clone libraries were constructed from pooled PCR products obtained from the cecal digesta of broilers avoided dietary vitamin additive (NV) and broilers with NRC level dietary vitamin additive (V).Sequence analysis revealed 188 and 185 clones for the two libraries, respectively.The 188 clones of NV library were assigned to 14 Operational Taxonomic Units (OTUs) with 33% clones affiliated with genus Clostridium, 19% genus Escherichia/Shigella and 14% genus Bacteroides.The 185 clones of V library were assigned to 23 OTUs with 46% clones affiliated with genus Clostridium and 11% with genus Faecalibacterium.Only 3OTUs assigned to Clostridium, Faecalibacterium and Ruminoccus, respectively, shared by the two libraries.Five bacterial genera (Escherichia/Shigella, Bacteroides, Subdoligranulum, Streptococcus and Parasporobacterium) were only found in the NV library, and eight genera (Anaerofilum, Lactobacillus, Anaerotruncus, Oscillibacter, Alistipes, Gracilibacter, Acetivibrio and Haloplasma) were only found in the V libarary.Shannon diversity index showed the V library exhibited significantly higher bacterial diversity (P =0.05) and Libshuff analysis indicated the differences in the community structure between the two libraries were significant (P <0.0001).Quantitative real-time PCR revealed that V broilers harbored significantly higher density of total bacteria, Lactobacillus and Clostridium leptum group and lower density of Enterobacteriaceae family and Veillonella spp.(P <0.01).(Conclusion) These differences illustrates that lack of dietary vitamin can increase the abundance of pathogenic or conditional pathogenic bacteria and reduce the diversity of bacteria in the cecum of broilers, which in turn impact the health and resistance of intestine.The results of current study provide new leads for further investigations on the interaction between dietary vitamin additive and gut health of host.