Abstract: [Objective] To study the effect of feeding fermented cottonseed meal on the number of bacteria and diversity in Angus beef cattle manure.[Method]The number of bacteria was calculated by plate counting method, V6-V8 DNA gene amplification of bacterial 16S rDNA was performed by PCR technique.The PCR products were subjected to denaturing gradient gel electrophoresis (DGGE).The specific bands of fingerprint were obtained and sequenced, and bacterial strains were identified by BLAST.[Result](1) In early experiment, there were significant differences in total bacteria, Escherichia coli and Lactobacillus between group C and group T (P < 0.05), but no significant difference in Staphylococcus aureus between them (P> 0.05).In late experiment, there was no significant difference in total bacteria between group C and group T (P> 0.05), but Escherichia coli, Staphylococcus aureus and Lactobacillus were significantly different (P< 0.05).(2) Bacteria found in cow dung were: Salmonella, Ruminococcus, Lactobacillus, Lachnospiraceae, Shigella, Clostridium, Escherichia coli, Enterobacter and Enterococcus, and among them, Lactobacillus and Escherichia coli might be the dominant bacteria in cow manure.[Conclusion]Total bacteria, Escherichia coli and Staphylococcus aureus have obvious change in the number of early and late experiment period.There are many kinds of bacteria in cow dung, which reflect the diversity of microbial flora in cow manure.