Objective:　To　analyze　the　molecular　epidemiological　characteristic　of　HIV-1　B＇/C　strains　prevalent　in　Beijing.　Methods:　Plasma　samples　were　collected　from　200　newly　diagnosed　HTV-1　B＇/C　individuals　reported　during　2006　to　2010　in　Beijing.　The　gag　gene　fragments　were　amplified　from　RNA　template　extracted　from　plasma　with　reverse　transcription　(RT)　and　nested　polymerase　chain　reaction　(PCR).　And　the　sequences　were　analyzed　by　phylogenetic　methods　and　Entropy　analysis.　Results:　A　total　of　159　sequences　were　successfully　amplified　from　the　gag　genes　of　which　147　was　CRF07_BC　and　12　CRF08_BC.　There　were　3　main　subclusters　in　CRF07_BC　phylogenetic　tree　and　they　were　named　as　subcluster　IDU-Vlax　(89　sequences),　subcluster　IDU-Min　(22　sequences)　and　subcluster　MSM　(34　sequences)　based　on　transmission.　No　international　reference　strain　was　closely　related　with　these　three　subclusters　except　ior　one　strain　identified　in　Taiwan.　All　CRF07_BC　recombinant　strains　were　remarkable　for　their　low　interpalient　diversity　in　gag　genes　(3.7%,　3.3%　and　2.0%　for　isolates　from　IDU-Max,　IDU-Min　and　MSM　respectively).　When　compared　with　subcluster　IDU-Max,　there　were　32　and　41　significantly　different　sites　of　nucleotide　polymorphism　compositions　in　subclusers　IDU-Min　and　MSM.　Conclusion:　This　is　the　first　report　of　describing　the　existence　of　three　main　epidemic　subclusters　in　CRF07_BC　strains　prevalent　in　Beijing.　And　IDU-Max　subcluster　is　the　dominant　strain.　The　CRF07_BC　in　Beijing　are　less　diverse　than　other　strains　and　may　be　derived　from　a　common　ancestor.　Copyright　©　2013　by　the　Chinese　Medical　Association.