〔Abstract〕 Objective To analyze the distribution characteristics of common capsular serotypes and virulence genes ofKlebsiella pneumoniaewith positive blood flow infection in the First Affiliated Hospital of Anhui Medical University, and to explore the correlation between virulence genes and CRISPR-CAS system. Methods 61 strains ofKlebsiella pneumoniaewere collected from blood culture bottles and identified asKlebsiella pneumoniae. The susceptibility ofKlebsiella pneumoniaeto commonly used antibiotics was detected by disk diffusion method and ViteK-compact 2 instrument.Klebsiella pneumoniaewith high mucus type were screened by wire drawing test. Six common capsular serotypes(K1, K2, K5, K20, K54, K57), seven virulence-related genes(rmpA, aerobactin, alls, Kfu, wcaG, magA, fimH) and three CRISPR-CAS system genes(CRISPR-1, CRISPR-2, CAS1) were detected by polymerase chain reaction(PCR). Results The serotypes of capsule were mainly K1 and K2, and the detection rates were 19.7% and 13.1% respectively. K5, K20 and K57 serotypes were detected in one case while K54 serotypes were not detected. The detection rates of virulence genes rmpA, aerobactin, alls, Kfu, wcaG, magA and fimH were 32.8%, 23.0%, 9.8%, 31.1%, 19.7%, 19.7% and 98.4%, respectively.14 strains were screened for high mucus phenotype. 11 strains were detected as positive by CRISPR-CAS system and the detection rate was 18%. Compared with the negative strains of CRISPR-CAS system, the virulence gene carrying rate of CRISPR-CAS system was higher, and the difference was statistically significant by χ2test(P<0.05). Conclusion K1 and K2 are the main serotypes ofKlebsiella pneumoniae. The virulence genes mainly exist in the strains with high mucus phenotype. The virulence gene carrying rate of CRISPR-CAS positive strains is high.